Organic Chemistry

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Organic Chemistry

• Unit 10

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What is Organic Chemistry?

• Organic chemistry is the study of carbon
  compounds.
• Besides carbon, the most common elements in
  organic compounds are hydrogen, oxygen,
  nitrogen, sulfur, and the halogens.

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Why is it Important?

• Animals, plants, and other forms of life consist
  of organic compounds.
• Organic products are found in foods, drugs,
  clothing, fuel, and many other products that we
  use everyday.
• Organic chemistry is an enormous field.
• gt90 of allcompoundsare organic.

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History of Organic Chemistry

• Scientists originally thought organic compounds
  contained a vital force due to their natural
  origin.
• Until 1828, when Friedrich Wöhler made urea
  (found in human urine) in the lab from a
  mineral.
• Today, many organic compounds are synthesized
  in the laboratory.

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Bonding in Organic Compounds

• Organic compounds are made of all non-metals, so
  they have covalent bonding.
• Their structures almost always obey the bonding
  rules in the following table

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Why Carbon is Unique

• Carbon forms 4 covalent bonds with a number of
  different elements, resulting in many different
  compounds.
• Carbon atoms readily form multiple bonds.
• Carbon, more than any other element, displays
  catenation the ability of an atom to form
  stable bonds with itself, joining up into
  chains or rings.

CnH2n2 n 1to ? (no limit) SinH2n2 n 1 to 6
only GenH2n2 n 1 to 3 only SnnH2n2 Only SnH4
exists
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Representing Organic Compounds

• Structural Formulas show all of the carbon and
  hydrogen atoms and how they are bonded together.
• Line-Angle (Carbon Skeleton) formulas do not show
  the hydrogen atoms that are bonded to carbons.
  Each angle, and beginning and end of a line,
  represents a carbon atom.
• Space-filling and ball-and-stick models are
  three-dimensional representations of the molecule.

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Formulas
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Isomers

• Isomers are different molecules with the same
  molecular formula.
• Structural Isomers (aka Constitutional Isomers)
  have a different pattern of atom attachment.
• Stereoisomers have the same atom attachments, but
  a different spatial orientation.

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Structural (Constitutional) Isomers

• Compounds with the same molecular formula but
  different structural formulas.
• Ex n-butane and isobutane both have the
  molecular formula of C4H10 but their structural
  formulas are quite different.

isobutane
C4H10
n-butane
C4H10
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Stereoisomers

• Different molecules whose atoms are connected in
  the same order, but have a different spatial
  orientation.
• optical isomers nonsuperimposable mirror
  images.
• Geometric (cis-trans) isomers cis means
  same side, trans means opposite side.

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IsomersSample Problem

• Write line-angle (carbon skeleton) formulas for
  the five isomers of C6H14.
• Use lines to represent each carbon-carbon bond.
  Remember that each end or bend represents a
  carbon atom.

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Hydrocarbons

• Hydrocarbons are the simplest organic compounds,
  containing only carbon and hydrogen.
• However, due to theuniqueness of carbon,there
  are many different kinds of hydrocarbons.
• Hydrocarbons are commonly used as fuels, and are
  the starting materials in the synthesis of many
  consumer products.

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Alkanes

• Alkanes are hydrocarbons that contain only single
  bonds.
• Alkanes are said to besaturated, because
  theirhydrogen content is at a maximum.
• Names all end in -ane.
• General formula is CnH2n 2
• Methane - butane are gases, Pentane - C17H36 are
  liquids, C18H38 higher are solids.
• Alkanes tend to be stable molecules, and not very
  reactive (other than combustion.)

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IUPAC Nomenclature

• Since there are so many organic compounds, a
  systematic methodof nomenclature is required.
• The system recommended by IUPAC (International
  Union of Pure and Applied Chemistry) is used
  throughout the world.
• Each name consists of 3 parts
• Prefix
• Parent
• Suffix

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Numbering the Base Chain
X

• Find the longest continuouscarbon chain.
• Number the chain from the end closest to a
  branch (substituent.)
• If 2 first branches are at equal distances from
  each end, use the next branch in to determine
  where to start.
• Use the appropriate base prefix, followed by the
  suffix-ane for an alkane.

Incorrect
X
Incorrect
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Alkyl Groups

• Name branches (substituents) as alkyl groups
  carbon-hydrogen groups with one less H than the
  corresponding alkane.
• The group does not exist independently but occurs
  bonded to another atom or molecule.
• In naming, the -ane is droppedand -yl is
  added. Ex methane becomes methyl.)

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Substituents

• a substituent is an atom or group of atoms
  substituted in place of a hydrogen atom on the
  parent chain of a hydrocarbon.
• Common substituents, other than alkyl groups, are
  oxygen, sulfur or nitrogen-based groups, and the
  halogens.

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Naming Substituents

• Locate each substituent by preceding its name
  with the carbon number on the chain
• List branches alphabetically
• do not count n-, sec-, t-, count iso
• Use prefix if morethan one of samegroup present
  (Ex di, tri, tetra, penta)
• Prefixes do not count in alphabetizing

1
3
2
4
6
5
7
8
9
nonane
5-ethyl-
4-isopropyl-
4-methyl
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Naming AlkanesSample Problem

• Write the correct IUPAC names for the following
  organic compounds
• a.)
• b.)

1
3
butane
2,2,3-trimethyl
1-bromo-
2
4
9
8
2
4
6
1
3
5
7
nonane
2,5,5,7-tetramethyl
3-ethyl-
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Cycloalkanes

• Cycloalkanes have rings of carbon atoms.
• They have the general formula CnH2n
• In carbon skeleton formulas, assume a C atom at
  each corner and enough Hs to give a total of 4
  single bonds to each C.

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Naming Cycloalkanes

• The ring is named by the number of carbons (as
  before) but with the prefix cyclo-.
• Number the ring starting from the carbon with the
  substituent lowest in the alphabet.
• Number in the direction that gives the lower
  overall substituent numbers. (To breaka tie,
  go in the direction that is alphabetical).

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Naming CycloalkanesSample Problem

• Write the correct IUPAC names for the following
  organic compounds
• a.)
• b.)

6
5
cyclohexane
chloro
1
4
2
3
2
3
1
1-isopropyl-
cyclopentane
3-methyl
4
5
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Alkenes Alkynes

• Alkenes have a double bond between 2 carbon
  atoms. General formula is CnH2n.
• Alkynes have a triple bond between 2 carbon
  atoms. General formula is CnH2n-2.
• Called unsaturated hydrocarbons since theyre not
  loaded to capacity with H.
• Much more reactive than alkanes.

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Naming Alkenes Alkynes

• Change suffix from -ane to -ene for base name
  of thealkene, or to -yne for base name of the
  alkyne.
• Number chain fromend closest to the multiple
  bond.
• Number in front of main name indicates first
  carbon of multiple bond.

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Naming Alkenes AlkynesSample Problem

• Write the correct IUPAC names for the following
  organic compounds
• a.)
• b.)

1
2
4
6
3
5
2-hexyne
4-methyl-
4
2
3
2-butene
trans-
1
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Classification of Hydrocarbons

• All of the hydrocarbons we have looked at so far
  are called aliphatic.
• There is another classification, called aromatic,
  which includes any hydrocarbon containing a
  benzene ring.

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Benzene

• The benzene molecule is composed of 6 carbon
  atoms joined in a ring, with 1 hydrogen atom
  attached to each carbon atom (C6H6.)
• A six-membered ring of carbon atoms with
  alternating single and double bonds was proposed
  for the structure of benzene by August Kekulé
  in1865.

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Benzene (contd.)

• However, properties of the benzene molecule and
  advanced bonding theory indicate that the
  electrons are actually shared by all the carbon
  atoms in the ring.

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Aromatic Compounds

• Aromatic hydrocarbonscontain one or more
  benzene rings.
• Although they are often drawn with CC bonds,
  they do not behave like alkenes.
• Many of these compounds have distinctive, often
  pleasant, aromas.
• when the benzene ring isnot the base name, it
  is called a phenyl group

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Naming Aromatic CompoundsSample Problem

• Write the correct IUPAC names for the following
  organic compounds
• a.)
• b.)

1
6
benzene
2,6-dichloro
1-bromo-
2
3
5
4
1
3
7
5
2
4
6
8
octane
1-phenyl
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Functional Groups

• A functional group is a characteristic atom or
  group of atoms inserted into a hydrocarbon.
• The presence of afunctional groupalters the
  propertiesof a compound, and determines
  thereactions it will participate in.
• since the type of hydrocarbon chain is irrelevant
  to the reactions, it may be indicated by the
  general symbol R

nonpolar
polar, H-bonded
gas
liquid
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Alcohols

• Alcohols are organic compounds containing a
  hydroxyl group(-OH).
• General formula is R-OH.
• IUPAC names end in -ol. Number the main chain
  from the end closest to -OH. Include the
  number of the -OH group.
• -OH groups are able to form hydrogen bondswith
  H2O, but the longer the hydrocarbon chain, the
  less soluble the alcohol is in water.

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Ethers

• Ethers are organic compounds with the general
  formula ROR.
• Diethyl ether is a common labsolvent, and was
  used as a general anesthetic.
• To name ethers, name each alkyl group attached
  to the O,then add ether to the end. List the R
  groups in alphabetical order. If they are the
  same, use di-.

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Aldehydes and Ketones

• Both aldehydes and ketonescontain the carbonyl
  group.
• Ketones have an R groupattached to both sides
  ofthe carbonyl group. IUPAC names end in -one.
• Aldehydes have at least one H atom attached to
  the carbonyl group. IUPAC names end in -al.

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Aldehydes and Ketones (contd)

• Many aldehydes and ketones have pleasant tastes
  and aromas.
• Some are pheromones.

Cinnamaldehyde 3-phenyl-2-propenal
Raspberry Ketone 4-(4-hydroxyphenyl)
butan-2-one
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Carboxylic Acids and Esters

• Carboxylic acids have the general formula RCOOH.
  Their IUPAC names end in -oic acid.
• Esters have the general formulaRCOOR. Their
  IUPAC names arebased on the corresponding
  carboxylic acid. Change the -ic acid ending to
  -ate. The R group replacing the H is named as an
  alkyl group.

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Carboxylic Acids and Esters (contd)

• Carboxylic acids are weak acids. Like all
  acids, they taste sour.
• Esters are best known for their sweet smells.

Citric Acid 2-hydroxypropane-1,2,3-t
ricarboxylic acid
Acetic Acid Ethanoic acid
Methyl Butanoate
Ethyl Butanoate
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Amines

• An amine is an organic compoundthat contains
  nitrogen, and can be thought of as a derivative
  of ammonia.
• Like ammonia, amines areweak bases.
• Amines form when proteins decompose, and are
  known for their awful odors.
• Name the alkyl groups attached to the N, then
  add -amine to the end.

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Naming w/ Functional GroupsSample Problem

• Write the correct IUPAC names for the following
  organic compounds
• a.)
• b.)

2
ether
phenyl
ethyl
1
propanoic acid
2-methyl
1
2
3
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Naming w/ Functional GroupsSample Problem
(Continued)

• Write the correct IUPAC names for the following
  organic compounds
• c.)
• d.)

amine
trimethyl
2-hexanol
3-methyl-
3
5
1
6
4
2
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Types of Organic Reactions

• Organic compounds participate in 3 main types of
  chemical reactions
• Substitution atom(s) of the starting material
  are replaced by other atom(s).
• Elimination - atoms of thestarting material
  arelost and a new ? bond is formed.
• Addition - atoms areadded to the starting
  material.

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Substitution Reactions

• Substitution reactions involve ? bonds one ?
  bond breaks and another forms at the same carbon
  atom.
• The atom being replaced is usually either a
  hydrogen or another atom more electronegative
  than carbon.

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Elimination Reactions

• In an elimination reaction, 2 groups (X Y) are
  removed from a starting material.
• Two ? bonds are broken, and a ? bond is formed
  between adjacent atoms.
• Most often, X is hydrogen and Y is an atom more
  electronegative than carbon.

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Addition Reactions

• In an addition reaction, 2 new groups (X Y) are
  added to the starting material. A ? bond is
  broken and 2 ? bonds are formed.
• Addition and elimination reactions are exact
  opposites. A ? bond is formed in elimination,
  and broken in addition.

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Types of Organic ReactionsSample Problem

• Classify each of the following as either
  substitution, elimination or addition reactions
• a.)
• b.)
• c.)

substitution
addition
elimination
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Polymers

• Polymers are long, chainlike molecules composed
  of repeating units.
• A monomer is the fundamental repeating unit of a
  polymer.

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Natural Polymers

• Natural Polymers play an important role in
  living organisms.
• Examples starches, proteins, and DNA.

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Synthetic Polymers

• Synthetics are man-made materials that have no
  duplicate in nature.
• The first synthetic polymer wasprepared by Leo
  Baekeland in 1907.
• Due to the scientific approach, chemists have
  been able to tailor new molecules for specific
  purposes.