Organic Functional Groups

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Unit 5

• Organic Functional Groups
• Alcohols, ethers esters carboxilic acids, amines

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2
3
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You need to recognize the benzene structure in
structural formulas
This is the general layout with a perfect
hexagon. In this particular diagram you do not
see the double bonds.
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Figure 20.7 Benzene C6H6.
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Two Lewis structures for the benzene ring.
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Shorthand notation for benzene rings.
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Some common mono-substituted benzene molecules
Toluene, sometimes you see this on marker pens
contains no toluene Has the condensed
structural formula C6H5CH3
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• IUPAC Substitutive Nomenclature
• An IUPAC name may have up to 4 features locants,
  prefixes, parent compound and suffixes
• Numbering generally starts from the end of the
  chain which is closest to the group named in the
  suffix

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Alcohols, Phenols and Thiols

• Alcohols have a general formula R-OH
• Phenols have a hdroxyl group attached directly to
  an aromatic ring
• Thiols and thiophenols are similar to alcohols
  and phenols, except the oxygen is replaced by
  sulfur

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Structures of Alcohols, Phenols, Thiols and Ethers

• Alcohols, phenols, thiols and ethers consist of a
  hydrocarbon singly bonded to an oxygen or a
  sulfur
• Alcohols have an -OH group attached to an alkane,
  phenols have an -OH group attached to a benzene,
  thiols have an -SH group attached to an alkane
  and ethers have an O bonded to two Cs

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Naming Alcohols

• Parent name ends in -ol
• Find longest chain containing the C to which the
  OH group is attached
• Number Cs starting at end nearest OH group
• Locate and number substituents and give full name
• - use a number to indicate position of OH group
• - cyclic alcohols have cyclo- before the parent
  name numbering begins at the OH group, going in
  direction that gives substituents lowest possible
  numbers
• - use a prefix (di-, tri-) to indicate multiple
  OH groups in a compound

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Nomenclature
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Unsaturated alcohols

• 2 endings are needed one for the double or
  triple bond and one for the hydroxyl group.
• The ol suffix comes last and takes precidence in
  numbering.

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Nomenclature Unsaturated alcohols

• CH2CHCH2OH Cyclohexanol
• 2-propen-1-ol
• phyenylmethanol
  

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Classification of Alcohols

• Alcohols can be classified as methyl, primary,
  secondary or tertiary
• Classification is based on the number of alkyl
  groups attached to the carbon to which the OH
  group is attached
• If OH is attached to a 1? C, its a 1? alcohol,
  etc.

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Naming Phenols

• Phenol is the common name for an OH group
  attached to a benzene, and is accepted by IUPAC
• Are usually named as derivatives of the parent
  compound
• Compounds with additional substituents are named
  as substituted phenols
• Ortho, meta and para are used when there is only
  one other substituent
• If there are two or more additional substituents,
  each must be numbered, beginning at the OH and
  going in direction that gives substituents lowest
  numbers (or alphabetical if same in both
  directions)

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Nomenclature of Phenols

• Phenol p-chlorophenol
• 2,4,6-tribromophenol

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Many phenols have pleasant odors, and some are
bioactive - Euganol (from cloves) is a topical
anesthetic - Thymol (from thyme) is an antiseptic
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• The hydroxyl group is named as a substituent when
  it occurs in the same molecule with carboxylic
  acid, aldehyde or ketone.

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• M-hydroxy benzoic acid
• P-hydroxybenzaldehyde

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Naming Thiols

• Parent name ends in -thiol
• Find longest chain containing the C to which the
  SH group is attached
• Number Cs starting at end nearest SH group
• Parent name is alkane name of carbon portion of
  longest chain, followed by thiol
• Locate and number substituents and give full name
• - use a number to indicate position of SH group
• - cyclic thiols have cyclo- before the parent
  name numbering begins at the SH group, going in
  direction that gives substituents lowest possible
  numbers
• - use a prefix (di-, tri-) to indicate multiple
  SH groups in a compound

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Naming Thiols

• CH3SH
• methanethiol
• 4,4-dimethyl-2-pentanethiol

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Thiols - Nomenclature

• Common names for simple thiols are derived by
  naming the alkyl group bonded to -SH and adding
  the word "mercaptan"

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Naming Ethers

• Simple ethers are named by their common names
• For common names name each alkyl group attached
  to the oxygen followed by ether
• For complex ethers IUPAC names are used
• For IUPAC names
• 1. Name as an alkane, with larger alkyl group
  being the parent chain
• 2. The smaller alkyl group and the O are named
  together as an alkoxy group (replace -yl with
  -oxy)
• 3. Number chain starting at end nearest alkoxy
  group
• 4. Use a number to give location of alkoxy group

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Naming Cyclic Ethers

• Cyclic ethers are generally named by their common
  names (we will not study the IUPAC names)
• A cyclic ether containing two carbons is called
  ethylene oxide (generally known as epoxides)
• A cyclic ether containing 4 carbons (with 2
  double bonds) is called a furan
• A cyclic ether containing 5 carbons (with 2
  double bonds) is called a pyran
• A cyclic ether containing 4 carbons and 2 oxygens
  is called a dioxane

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Naming Examples
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Physical Properties of Alcohols, Phenols, Thiols
and Ethers

• All of these types of compounds have a bent
  geometry around the O or the S, and are polar
  compounds
• Alcohols and phenols contain a very polarized O-H
  bond, and they can H-bond with themselves and
  with other alcohols or water
• - Small alcohols (4 or less Cs) are soluble in
  water
• While larger larger alcohols become
  insoluble
• - Phenol is soluble in water (even with 6 Cs)
  because it partially ionizes in water (its a
  weak acid)
• - Alcohols and phenols have relatively high
  boiling points

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• Thiols are much less polar than alcohols because
  the electronegativity of S is the same as that of
  C (2.5), much less than that of O (3.5), so C-S
  and S-H bonds are not polar
• - thiols do not H-bond and have relatively low
  boiling points
• Ethers do not H-bond with themselves, so have
  boiling points similar to hydrocarbons
• -ethers are only slightly soluble in water and
  are highly flammable

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Physical Properties

• bp increases as MW increases
• solubility in water decreases as MW increases

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Boiling Points of Alcohols

• Alcohols contain a strongly electronegative O in
  the OH groups.
• Thus, hydrogen bonds form between alcohol
  molecules.
• Hydrogen bonds contribute to higher boiling
  points for alcohols compared to alkanes and
  ethers of similar mass.

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Boiling Points of Ethers

• Ethers have an O atom, but there is no H
  attached.
• Thus, hydrogen bonds cannot form between ether
  molecules.

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Acidity and Basicity of Alcohols and Phenols

• Alcohols and phenols, like water, can act as
  either weak acids or weak bases (although phenol
  is more acidic) ( hydroxyl group can act as a
  proton donor)
• Phenols are more acidic because the anion that
  forms upon loss of the proton is stabilized by
  resonance

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Reactions of Alcohols

• Alcohols undergo combustion with O2 to produce
  CO2 and H2O.
• 2CH3OH 3O2 2CO2 4H2O Heat
• Dehydration removes H- and -OH from adjacent
  carbon atoms by heating with an acid catalyst.
• H OH
• H, heat
• HCCH HCCH H2O
• H H H H
• alcohol alkene

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Combustion Reactions of Alcohols and Ethers

• Both alcohols and ethers can burn with oxygen to
  produce water, carbon dioxide and heat (just like
  hydrocarbons)
• However, ethers are much more flammable than
  alcohols and care should be taken when working
  with ethers in the laboratory (just a spark from
  static electricity can set off ether fumes)
• Examples
• CH3CH2OH 3O2 ? 2CO2 3H2O
  Heat
• CH3-O-CH3 3O2 ? 2CO2 3H2O
  Heat

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Dehydration of Alcohols to Form Alkenes

• An alcohol can lose a water molecule to form an
  alkene using an acid catalyst such as H2SO4 and
  heat (an elimination reaction)
• This is the reverse of the addition of H2O to an
  alkene
• Dehydration is favored by using heat (endothermic
  reaction) and a solvent other than water (lower
  concentration of H2O)
• When more than one alkene can be formed,
  Zaitsevs rule states that the more substituted
  alkene will be the major product
• Order of reactivity 3? gt 2? gt (1? gt
  methyl)
• - In fact this reaction only works with 3? and
  2? alcohols

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Mechanism of Acid-Catalyzed Dehydration of an
Alcohol

• First, the acid catalyst protonates the alcohol
• Next, H2O is eliminated to form a carbocation
• Finally, a proton is removed to form an alkene
  H3O

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• The important things to remember about alcohol
  dehydration are that
• 1. they all begin by protonation of a hydroxyl
  group
• 2. the ease of alcohol dehydration is
• 3gt2gt1 ( tertiary to primary)

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Reaction of alcohols with hydrogen halides

• Alcohols react with hydrogen halides (HCl, HBr,
  HI) to give alkyl halides
• (CH3)3COH H-Cl ----- (CH3)3C-Cl H-OH
• t-butyl alcohol t-butyl chloride

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Formation of Ethers

• Ethers form when dehydration takes place at low
  temperature.
• H
• CH3OH HOCH3 CH3OCH3 H2O
• Two Methanol Dimethyl ether

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Oxidation and Reduction

• In organic chemistry, oxidation is a loss of
  hydrogen atoms or a gain of oxygen.
• In an oxidation, there is an increase in the
  number of C-O bonds.
• Reduction is a gain of hydrogen or a loss of
  oxygen. The number of C-O bonds decreases.

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Oxidation of Primary Alcohols

• In the oxidation O of a primary alcohol, one H
  is lost from the OH and another H from the
  carbon bonded to the OH.
• O
• Primary alcohol Aldehyde
• OH O
• O
• CH3CH CH3CH H2O
• H
• Ethanol Ethanal
• (ethyl alcohol) (acetaldehyde)

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Oxidation of Secondary Alcohols

• The oxidation of a secondary alcohol removes one
  H from OH and another H from the carbon bonded
  to the OH.
• O
• Secondary alcohol Ketone
• OH O
• O
• CH3CCH3 CH3CCH3 H2O
• H
• 2-Propanol Propanone
• (Isopropyl alcohol) (Dimethylketone
  Acetone)

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Oxidation of Tertiary Alcohols

• Tertiary alcohols are resistant to
  oxidation. O
• Tertiary alcohols no reaction
• OH
• O
• CH3CCH3 no product
• CH3 no H on the C-OH to
  oxidize
• 2-Methyl-2-propanol

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Ethanol CH3CH2OH

• Ethanol
• Acts as a depressant.
• Kills or disables more people than any other
  drug.
• Is metabolized at a rate of 12-15 mg/dL per hour
  by a social drinker.
• Is metabolized at a rate of 30 mg/dL per hour by
  an alcoholic.

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Oxidation of Alcohol in the Body

• Enzymes in the liver oxidize ethanol.
• The aldehyde produced impairs coordination.
• A blood alcohol level over 0.4 can be fatal.
  O
  
  CH3CH2OH CH3CH 2CO2
  H2OEthyl alcohol acetaldehyde

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Oxidation of alcohols in liver
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Effect of Alcohol on the Body

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Breathalyzer test

• K2Cr2O7 (potassium dichromate)
• This orange colored solution is used in the
  Breathalyzer test (test for blood alcohol level)
• Potassium dichromate changes color when it is
  reduced by alcohol
• K2Cr2O7 oxidizes the alcohol

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Breathalyzer reaction

• orange-red green
• 8HCr2O72-3C2H5OH?2Cr33C2H4O7H2O
• dichromate ethyl chromium
  (III) acetaldehyde
• ion alcohol ion
• (from K2Cr2O7)

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Alcohol Contents in Common Products

• Ethanol Product
• 50 Whiskey, rum, brandy
• 40 Flavoring extracts
• 15-25 Listerine, Nyquil, Scope
• 12 Wine, Dristan, Cepacol
• 3-9 Beer, Lavoris

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The proof of an alcohol

• The proof of an alcoholic beverage is merely
  twice the percentage of alcohol by volume.
• The term has its origin in an old
  seventeenth-century English method for testing
  whiskey.
• Dealers were often tempted to increase profits by
  adding water to booze.
• A qualitative method for testing the whiskey was
  to pour some of it on gunpowder and ignite it.
• If the gunpowder ignited after the alcohol had
  burned away, this was considered proof that the
  whiskey did not contain too much water.

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Preparation of alcohols

• Ethanol is made by hydration of ethylene (ethene)
  in the presence of acid catalyst

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Isopropyl

• is produced by addition of water to propylene
  (1-propene)

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Methanol

• is made commercially from carbon monoxide and
  hydrogen
• CO 2H2 ? CH3OH

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Oxidation of Thiols.

• Mild oxidizing agents remove two hydrogen atoms
  from two thiol molecules.
• The remaining pieces of thiols combine to form a
  new molecule, disulfide, with a covalent bond
  between two sulfur atoms.
• R S H H S RI2 ? RS SR2HI
• 2 RSH H2O2 ? RS SR 2 H2O

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The chemistry of the permanent waving of hair.

• Hair is protein, and it is held in shape by
  disulfide linkages between adjacent protein
  chains.
• The first step involves the use of lotion
  containing a reducing agent such as thioglycolic
  acid, HS CH2 COOH.
• The wave lotion ruptures the disulfide linkages
  of the hair protein.
• The hair is then set on curles or rollers and is
  treated with a mild oxidizing agent such as
  hydrogen peroxide (H2O2).
• Disulfide linkages are formed in new positions to
  give new shape to the hair.
• Exactly the same chemical process can be used to
  straighten naturally curly hair.
• The change in hair style depends only on how one
  arranges the hair after the disulfide bonds have
  been reduced and before the reoxidation takes
  place.

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Ethers and Epoxides and Sulfides
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Ethers and Their Relatives

• An ether has two organic groups (alkyl, aryl, or
  vinyl) bonded to the same oxygen atom, ROR?
• Diethyl ether is used industrially as a solvent
• Tetrahydrofuran (THF) is a solvent that is a
  cyclic ether
• Thiols (RSH) and sulfides (RSR?) are sulfur
  (for oxygen) analogs of alcohols and ethers

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18.1 Names and Properties of Ethers

• Simple ethers are named by identifying the two
  organic substituents and adding the word ether
• If other functional groups are present, the ether
  part is considered an alkoxy substituent
• ROR tetrahedral bond angle (112 in dimethyl
  ether)
• Oxygen is sp3-hybridized
• Oxygen atom gives ethers a slight dipole moment

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Physical Properties of ethers

• They have a lower boiling point than alcohols
• They cannot form hydrogen bonds with one another.
• Ethers are less dense than water
• Alcohols and ethers are usually mutually soluble.
• Ethers are relatively inert compounds, making
  ethers excellent solvents in organic reactions.

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Grignard Reagent

• One example of the solvating power of ethers is
  in the preparation of Grignard reagents.
• These reagents are useful in organic synthesis
• Was discovered in 1912 by Victor Grignard
• These reagents are alkyl or arylmagnesium
  halidesAre organometallic compounds because they
  contain a carbon-metal bond

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Grignard Reagent

• Grignard found that when magnesium turnings are
  stirred with ether solution of an alkyl or aryl
  haide, an exothermic reaction occurs
• R-X Mg dry ether R-MgX
• gringard
  reagent
• Gringard reagents usually react if the alkyl or
  aryl group is negatively charged ( carbanion) and
  the magnesium is positively charged

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Formation of Ethers by dehydration of alcohols

• Ethers form when dehydration takes place at low
  temperature.
• H
• CH3OH HOCH3 CH3OCH3 H2O
• Two Methanol Dimethyl ether

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18.2 Synthesis of Ethers

• Diethyl ether prepared industrially by sulfuric
  acidcatalyzed dehydration of ethanol also with
  other primary alcohols

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The Williamson Ether Synthesis

• Reaction forming an ether from an organohalide
  and an alcohol
• Best method for the preparation of ethers
• Alkoxides prepared by reaction of an alcohol with
  a strong base such as sodium hydride, NaH

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Silver Oxide-Catalyzed Ether Formation

• Reaction of alcohols with Ag2O directly with
  alkyl halide forms ether in one step
• Glucose reacts with excess iodomethane in the
  presence of Ag2O to generate a pentaether in 85
  yield

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Alkoxymercuration of Alkenes

• React alkene with an alcohol and mercuric acetate
  or trifluoroacetate
• Demercuration with NaBH4 yields an ether
• Overall Markovnikov addition of alcohol to alkene

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Reactions of Ethers Acidic Cleavage

• Ethers are generally unreactive
• Strong acid will cleave an ether at elevated
  temperature
• HI, HBr produce an alkyl halide from less
  hindered component by SN2 (tertiary ethers
  undergo SN1)

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18.4 Reactions of Ethers Claisen Rearrangement

• Specific to allyl aryl ethers, ArOCH2CHCH2
• Heating to 200250C leads to an o-allylphenol
• Result is alkylation of the phenol in an ortho
  position

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Claisen Rearrangement Mechanism

• Concerted pericyclic 6-electron, 6-membered ring
  transition state
• Mechanism consistent with 14C labeling

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Cyclic Ethers Epoxides

• Cyclic ethers behave like acyclic ethers, except
  if ring is 3-membered
• Dioxane and tetrahydrofuran are used as solvents

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Epoxides (Oxiranes)

• Cyclic ethers with a three-membered ring
  containing one oxygen atom also called oxiranes
• Three membered ring ether is called an oxirane
  (root ir from tri for 3-membered prefix ox
  for oxygen ane for saturated)
• Also called epoxides
• Ethylene oxide (oxirane 1,2-epoxyethane) is
  industrially important as an intermediate
• Prepared by reaction of ethylene with oxygen at
  300 C and silver oxide catalyst

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Preparation of Epoxides Using a Peroxyacid

• Treat an alkene with a peroxyacid

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Epoxides from Halohydrins

• Addition of HO-X to an alkene gives a halohydrin
• Treatment of a halohydrin with base gives an
  epoxide
• Intramolecular Williamson ether synthesis

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18.6 Reactions of Epoxides Ring-Opening

• Water adds to epoxides with dilute acid at room
  temperature
• Product is a 1,2-diol (on adjacent Cs vicinal)
• Mechanism acid protonates oxygen and water adds
  to opposite side (trans addition)

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Halohydrins from Epoxides

• Anhydrous HF, HBr, HCl, or HI combines with an
  epoxide
• Gives trans product

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Regiochemistry of Acid-Catalyzed Opening of
Epoxides

• Nucleophile preferably adds to less hindered site
  if primary and secondary Cs
• Also at tertiary because of carbocation character
  (See Figure 18.2)

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Base-Catalyzed Epoxide Opening

• Strain of the three-membered ring is relieved on
  ring-opening
• Hydroxide cleaves epoxides at elevated
  temperatures to give trans 1,2-diols

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Addition of Grignards to Ethylene Oxide

• Adds CH2CH2OH to the Grignard reagents
  hydrocarbon chain
• Acyclic and other larger ring ethers do not react

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18.7 Crown Ethers

• Large rings consisting repeating (-OCH2CH2-) or
  similar units
• Named as x-crown-y
• x is the total number of atoms in the ring
• y is the number of oxygen atoms
• 18-crown-6 ether 18-membered ring containing 6
  oxygen atoms
• Central cavity is electronegative and attracts
  cations

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Sulfides

• Sulfides (RSR?), are sulfur analogs of ethers
• Named by rules used for ethers, with sulfide in
  place of ether for simple compounds and alkylthio
  in place of alkoxy

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Sulfides

• Thiolates (RS?) are formed by the reaction of a
  thiol with a base
• Thiolates react with primary or secondary alkyl
  halide to give sulfides (RSR)
• Thiolates are excellent nucleophiles and react
  with many electrophiles

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Aldehydes and Ketones
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Carbonyl Group

                                          

• Carbon atom joined to oxygen by a double bond.
• Characteristic of
• Ketones
• Aldehydes

            
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Aldehydes

• Comes from alcohol dehydrogenation
• Obtained by removing of a hydrogen from an
  alcohol
• The CHO group is called a formyl group

                                                      
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Aldehydes

• Both common and IUPAC names frequently used
• Common names from acids from which aldehydes can
  be converted

                                                           
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Aldehydes

• IUPAC
• Longest chain with aldehyde
• Drop e and add -al
• Aldehyde takes precedence over all other groups
  so far
• Examples

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Common Aldehyde names

• Formaldehyde Ethanal
  (acetaldehyde)
• Propanal (propionaldehyde) Butanal
  (n-butyraldehyde)

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Aldehyde group has priority over double bonds or
hydroxyl group

• Cyclopentanecarbaldehyde Benzaldehyde
• salicylaldehyde

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• Aldehydes are commonly detected by means of the
  Wagner Test ( which is composed of 2 grams of
  iodine and 6 grams of KI dissolved in 100 ml of
  water)
• Positive results produce a brown or reddish brown
  precipitant

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Ketones

                                                                      

• Naming
• Drop e, add -one
• Many common names
• Simplest is 3 carbons
• C. name acetone
• IUPAC propanone

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Ketones

• Carbonyl carbon gets lowest number
• See examples
• Acetone 2-butanone 3-pentanone
• (ethyl methyl ketone)
  (diethyl ketone)

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• O
• CH2CH-C-CH3
• 3-buten-2-one 2-methylcyclopentanone
• Cyclohexanone acetophenone
• 
  (methyl phenyl ketone)

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• Benzophenone dicyclopropyl ketone
• (diphenyl ketone)

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Common Carbonyl Compounds

• Formaldehyde (simplest aldehyde)
• Manufactured from methanol
• Used in many polymers
• Acetaldehyde
• Prepared from ethyl alcohol
• Formed in the detoxification of alcohol in the
  liver
• Acetone (simplest ketone)
• Formed in the human body as a by-product of lipid
  metabolism
• Excreted in the urine
• Hormones
• Steroid hormones
• Progesterone/Testosterone

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Physical Properties of Aldehydes and Ketones

• Carbon-oxygen double bond is very polar
• Affects boiling points
• More than ethers (C-O bonds)
• Less than alcohols (C-OH bonds)
• Odors
• Low aldehydes very pungent
• High aldehydes pleasant odors (perfumes)
• Solubility
• Similar to alcohols and ethers
• Soluble up to about 4 carbons
• Insoluble after that

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Quinones

• Unique class of carbonyl compounds
• Are cyclic conjugated diketones
• Simplest ex is 1,4 benzoquinone
• Example vitamin k

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Alizarin

• Alizarin orange red quinone used to dye red
  coats of British army during American revolution

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Preparations of Aldehydes and ketones

• ALDEHYDE
• 1. oxidation
• 2. reduction
• 3. hydration

• KETONE
• 1. oxidation
• 2. reduction
• 3. hydrolysis

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Preparation of Aldehydes

• Oxidation
• Leads to carboxylic acid unless care is taken
• 1 alcohols

                                           
                                                                                  
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Preparation of Ketones

• Oxidation of a 2 alcohol
• Utilizes chromium compounds and sulfuric acid

                              
                                
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Chemical Properties of Aldehydes and Ketones

• Both under-go combustion reactions
• Oxidation
• Aldehydes can be oxidized, ketones cant
• Tollens reagent
• Benedicts reagent
• Fehlings reagent

 
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Chemical Properties of Aldehydes and Ketones

                                            

• Reduction
• Variety of agents can reduce aldehydes and
  ketones to alcohols
• NaBH4 and H2 commonly used

                                                                
                                     
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Chemical Properties of Aldehydes and Ketones

• Hydration
• Formaldehyde dissolves readily in water
• Acetaldehyde somewhat also
• Form hydrates

                                   
                                         

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Chemical Properties of Aldehydes and Ketones

                                       

                                       

• Addition of Alcohols to Carbonyl Groups
• Hemiacetal
• Aldehyde alcohol
• Hemiketal
• Ketone alcohol
• Not very stable
• Differs from
• 1 mol to 2 mol

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Chemical Properties of Aldehydes and Ketones

• Hemiacetals HCl acetal (caused by presence of
  excess alcohol)
• Hemiketal HCl ketal

                                                             
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Keto-Enol Tautomerism

• Aldehydes and ketones may exist as an equilibrium
  mixture of 2 forms, called the keto form and the
  enol form.
• The two forms differ in the locaiton of the
  protons and a double bond
• This type f structural isomerism is called a
  tautomerism.
• The two forms of the aldehyde or ketone are
  called tautomers. ( structural isomers)
• Most simple aldehydes and ketones exist mainly in
  the keto form.

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Keto-Enol Tautomerism

• H O
  OH
• -C-C- CC
• Keto form Enol form

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Carboxylic acids
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Structure of carboxylic acids and their
derivatives

• The functional group present in a carboxylic acid
  is a combination of a carbonyl group and a
  hydroxyl group however, the resulting carboxyl
  group ( -COOH) possesses properties that are
  unlike those present in aldehydes/ketones and
  alcohols.

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Structure of carboxylic acids and their
derivatives

• Carboxylic acids have the following general
  formula
• Some simple carboxylic acids
• Since carbon can have only four bonds, there are
  no cyclic carboxylic acids (i.e. the carboxyl
  group cannot form part of a carbon ring)

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Structure of carboxylic acids and their
derivatives

• The following molecules have a similar structure
  to carboxylic acids, and will be encountered in
  this unit and the next.

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Carboxyl Group

• Carboxylic acids contain the carboxyl group on
  carbon 1.
• O
• ??
• CH3 COH CH3COOH
• carboxyl group

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IUPAC nomenclature for carboxylic acids

• For monocarboxylic acids (one COOH group)
• Select the longest, continuous carbon chain that
  involves the carboxyl group. This is the parent
  chain and the COOH carbon is designated as C-1.
• Name the parent chain by dropping the e from
  the corresponding alkane name and changing to
  oic acid
• Indicate the identity and location of
  substituents on the parent chain at the front of
  the carboxylic acids name

Benzoic acid
122
IUPAC nomenclature for carboxylic acids

• Dicarboxylic acids
• For these compounds, both ends of a chain will
  end with a COOH group. The parent chain is the
  one that involves both COOH groups.
• The parent chain is named as an alkane and the
  term dioic acid is added afterwards to indicate
  the diacid structure.

123
Common names for carboxylic acids
124
Common names for dicarboxylic acids
125
Common names for carboxylic acids

• For common-name carboxylic acids and diacids,
  substituents are often numbered using a Greek
  system
• So the following molecule could be called
  a-Methylpropionic acid (or, using the IUPAC
  system, 2-Methylpropanoic acid)

126
5 4 3 2 1 CCCCCO d ?
ß a used in common names
127
Special names!
128
Naming Carboxylic Acids

• Formula IUPAC Common
• alkan -oic acid prefix ic acid
• HCOOH methanoic acid formic acid
• CH3COOH ethanoic acid acetic acid
• CH3CH2COOH propanoic acid propionic acid
• CH3CH2CH2COOH butanoic acid butyric acid

129
Naming Rules

• Identify longest chain
• (IUPAC) Number carboxyl carbon as 1
• (Common) Assign ?, ?, ? to carbon atoms adjacent
  to carboxyl carbon
• CH3
• CH3 CHCH2 COOH
• IUPAC 3-methylbutanoic acid
• Common ?-methylbutryic acid

130
Polyfunctional carboxylic acids

• Carboxylic acids that contain other functional
  groups besides the COOH group are called
  polyfunctional carboxylic acids. Some examples
  are shown below

131
Properties

• Carboxylic acids are weak acids
• CH3COOH H2O CH3COO H3O
• Neutralized by a base
• CH3COOH NaOH CH3COO Na H2O

132
Physical properties polar, no hydrogen
bonding mp/bp are relatively moderate for
covalent substances water insoluble (except
four-carbons or less)
133
RCO2H RCO2- covalent ionic water
insoluble water soluble Carboxylic acids are
insoluble in water, but soluble in 5 NaOH.
134
Preparation of carboxylic acids

• We saw in earlier that carboxylic acids can be
  prepared from aldehydes (which can be prepared
  from primary alcohols)
• Aromatic carboxylic acids can be made by
  oxidizing alkyl-substituted aromatic molecules

135
Acidity of carboxylic acids

• When carboxylic acids are placed in water, they
  undergo de-protonation as discussed in Ch-10

• When carboxylic acids are placed in water, they
  undergo de-protonation as discussed earlier

Remember from Ch-10 HA H2O D A- H3O
136
Acidity of carboxylic acids
137
Carboxylic acid salts

• When carboxylic acids are reacted with strong
  bases, they are converted to salts as follows

138
Carboxylic acid salts

• Salts of carboxylic acids are much more
  water-soluble than the acids themselves. Also,
  they can be converted back to the acid form by
  reacting them with a strong acid

139

• Carboxylic acids, syntheses
• oxidation of primary alcohols
• RCH2OH K2Cr2O7
• RCOOH
• 2. oxidation of arenes
• ArR KMnO4, heat ? ArCOOH
• 3. carbonation of Grignard reagents
• RMgX CO2 ? RCO2MgX H ?
  RCOOH
• 4. hydrolysis of nitriles (alkyl cyanide)
• RCN H2O, H, heat ? RCOOH

140

• oxidation of 1o alcohols most common oxidizing
  agents are potassium permanganate, chromic acid
  anhydride, nitric acid
• CH3CH2CH2CH2-OH CrO3 ? CH3CH2CH2CO2H
• n-butyl alcohol butyric acid
• 1-butanol butanoic acid
• CH3
  CH3
• CH3CHCH2-OH KMnO4 ? CH3CHCOOH
• isobutyl alcohol isobutyric acid
• 2-methyl-1-propanol 2-methylpropanoic acid

141

• oxidation of arenes

note aromatic acids only!
142

• carbonation of Grignard reagent
• R-X RMgX RCO2MgX RCOOH
• Increases the carbon chain by one carbon.
• Mg
  CO2 H
• CH3CH2CH2-Br CH3CH2CH2MgBr
  CH3CH2CH2COOH
• n-propyl bromide butyric acid

Mg CO2
H
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• Hydrolysis of a nitrile
• H2O, H
• R-C?N R-CO2H
• heat
• H2O, OH-
• R-C?N R-CO2- H ? R-CO2H
• heat
• R-X NaCN ? R-CN H, H2O, heat ?
  RCOOH
• 1o alkyl halide
• Adds one more carbon to the chain.
• R-X must be 1o or CH3!

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• carboxylic acids, reactions
• as acids
• conversion into functional derivatives
• a) ? acid chlorides
• b) ? esters
• c) ? amides
• reduction
• alpha-halogenation
• EAS

148

• as acids
• with active metals
• RCO2H Na ? RCO2-Na H2(g)
• with bases
• RCO2H NaOH ? RCO2-Na H2O
• relative acid strength?
• CH4 lt NH3 lt HC?CH lt ROH lt HOH lt H2CO3 lt RCO2H lt
  HF
• quantitative
• HA H2O ? H3O A-
  ionization in water
• Ka H3O A- / HA

149

• Conversion into functional derivatives
• ? acid chlorides

150

• ? esters
• direct esterification
  H
• RCOOH ROH ? RCO2R
  H2O
• -reversible and often does not favor the ester
• -use an excess of the alcohol or acid to shift
  equilibrium
• -or remove the products to shift equilibrium to
  completion
• indirect esterification
• RCOOH PCl3 ? RCOCl ROH ?
  RCO2R
• -convert the acid into the acid chloride first
  not reversible

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• ? amides
• indirect only!
• RCOOH SOCl2 ? RCOCl NH3 ?
  RCONH2
• 
  amide
• Directly reacting ammonia with a carboxylic acid
  results in an ammonium salt
• RCOOH NH3 ? RCOO-NH4
• acid base
  

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• Reduction
• RCO2H LiAlH4 then H ? RCH2OH
• 1o alcohol
• Carboxylic acids resist catalytic reduction under
  normal conditions.
• RCOOH H2, Ni ? NR

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• Alpha-halogenation (Hell-Volhard-Zelinsky
  reaction)
• RCH2COOH X2, P ? RCHCOOH HX
• 
  X
• 
  a-haloacid
• X2 Cl2, Br2

157
5. EAS (-COOH is deactivating and meta-
directing)
158

• carboxylic acids, reactions
• as acids
• conversion into functional derivatives
• a) ? acid chlorides
• b) ? esters
• c) ? amides
• reduction
• alpha-halogenation
• EAS

159
Esters
160
Esters

• In and ester, the H in the carboxyl group is
  replaced with an alkyl group
• O
• ??
• CH3 CO CH3 CH3COO CH3
• ester group

161
Esters in Plants

• Esters give flowers and fruits their pleasant
  fragances and flavors.

162
Naming esters

• The alcohol part of the name comes first and the
  carboxylic part second
• For example CH3COOCH3 is made from CH3COOH and
  CH3OH. i.e Ethanoic acid and methanol
• Its name is Methyl ethanoate

162
163
Naming Esters

• Name the alkyl from the alcohol O-
• Name the acid with the CO with ate
• acid alcohol
• O
• ?? methyl
• CH3 CO CH3
• Ethanoate methyl ethanoate (IUPAC)
• (acetate) methyl acetate (common)

164
Some Esters and Their Names

• Flavor/Odor
• Raspberries
• HCOOCH2CH3 ethyl methanoate (IUPAC)
• ethyl formate (common)
• Pineapples
• CH3CH2CH2 COOCH2CH3
• ethyl butanoate (IUPAC)
• ethyl butyrate (common)

165
esters

• Give the IUPAC and common names of the following
  compound, which is responsible for the flavor and
  odor of pears.
• O
• ??
• CH3 CO CH2CH2CH3

166
Solution

• O
• ?? propyl
• CH3 CO CH2CH2CH3
• propyl ethanoate (IUPAC)
• propyl acetate (common)

167

• Draw the structure of the following compounds
• 3-bromobutanoic acid
• Ethyl propionoate

168
Solution

• A. 3-bromobutanoic acid
• Br
• CH3CHCH2COOH
• B. Ethyl propionoate
• O
• ??
• CH3 CH2 COCH2CH3 CH3CH2COOCH2CH3

169
Chemical reactions of esters

• Ester hydrolysis the hydrolysis of an ester is
  accomplished by reacting water with the ester in
  the presence of an acid catalyst (this is the
  reverse reaction of esterification).
• An example

170
Chemical reactions of esters

• Ester saponification another hydrolysis
  reaction, but this time, under basic conditions.
  Rather than a carboxylic acid, the acid salt is
  produced here.
• Example

171
Sulfur analogs of esters

• Earlier we saw sulfur analogs of alcohols,
  ethers, aldehydes, and ketones. Esters also have
  known sulfur analogs, thioesters
• Thioesters are made by condensation reactions
  involving carboxylic acids and thiols.

172
Sulfur analogs of esters

• Thioesters, like esters, have relatively low
  boiling points (compared to alcohols and
  carboxylic acids) and may be found in foods as
  flavorings.
• Acetyl coenzyme A, a thioester, is important in
  metabolic cycles that provide our bodies with
  energy.

Methyl thiobutanoate
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Esterification

• Reaction of a carboxylic acid and alcohol
• Acid catalyst
• O
• ?? H
• CH3 COH HOCH2CH3
• O
• ??
• CH3 COCH2CH3 H2O

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Hydrolysis

• Esters react with water and acid catalyst
• Split into carboxylic acid and alcohol
• O
• ?? H
• H COCH2CH3 H2O
• O
• ??
• H COH HOCH2CH3

175
Saponification

• Esters react with a bases
• Produce the salt of the carboxylic acid and
  alcohol
• O
• ??
• CH3COCH2CH3 NaOH
• O
• ??
• CH3CO Na HOCH2CH3
• salt of carboxylic acid

176
Amines

• Organic bases derived from ammonia

177

• Primary, secondary or tertiary depending on
  whether 1, 2, or 3 organic groups are attached to
  the nitrogen.
• H-N-H R-N-H R-N-R R-N-R
• H H H
  R
• ammonia primary
  secondary tertiary

178
Amines (organic ammonia) NH3 NH2R or
RNH2 1o amine (R may be Ar) NHR2 or R2NH 2o
amine NR3 or R3N 3o amine NR4 4o ammonium
salt
179
amines are classified by the class of the
nitrogen, primary amines have one carbon bonded
to N, secondary amines have two carbons attached
directly to the N, etc. Nomenclature. Common
aliphatic amines are named as alkylamines
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Amines, physical properties Nitrogen is sp3
hybridized, amines are polar and can hydrogen
bond. mp/bp are relatively high for covalent
substances amines are basic and will turn litmus
blue insoluble in water (except for
four-carbons or less) soluble in 5 HCl fishy
smell ?
183
Types of reactions

• 1. preparation of amines
• Ammonia reacts with alkyl halide to give an amine
• NH3 CH3Cl -------- CH2-NH3 Cl

184
RNH2 HCl ? RNH3 Cl- water
water insoluble
soluble RNH3 OH- ? RNH2 H2O
water
water soluble insoluble
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Types of reactions

• 2. Reduction of Nitrogen compound
• Ar-NO2 H2,Ni ? Ar-NH2

187
Reduction of nitro compounds
188

• Amines, syntheses
• Reduction of nitro compounds
• Ar-NO2 H2,Ni ? Ar-NH2
• Ammonolysis of 1o or methyl halides
• R-X NH3 ? R-NH2
• Reductive amination
• R2CO NH3, H2, Ni ? R2CHNH2
• Reduction of nitriles
• R-C?N 2 H2, Ni ? RCH2NH2
• Hofmann degradation of amides
• RCONH2 KOBr ? RNH2

189

1. Ammonolysis of 1o or methyl halides.

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192
3. Reductive amination
Avoids E2
193
Reductive amination via the imine.
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• Reduction of nitriles
• R-C?N 2 H2, catalyst ? R-CH2NH2
• 1o amine
• R-X NaCN ? R-CN ? RCH2NH2
• primary amine with one additional carbon
• (R must be 1o or methyl)

196
5. Hofmann degradation of amides
197

• Amines, syntheses
• Reduction of nitro compounds 1o Ar
• Ar-NO2 H2,Ni ? Ar-NH2
• Ammonolysis of 1o or methyl halides R-X 1o,CH3
• R-X NH3 ? R-NH2
• Reductive amination avoids E2
• R2CO NH3, H2, Ni ? R2CHNH2
• Reduction of nitriles 1 carbon
• R-C?N 2 H2, Ni ? RCH2NH2
• Hofmann degradation of amides - 1 carbon
• RCONH2 KOBr ? RNH2