Chapter 19: Organic chemistry

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Chapter 19 Organic chemistry
Chemistry 1020 Interpretive chemistry Andy
Aspaas, Instructor
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Organic compounds

• Organic compounds carbon containing compounds
• Specifically, with carbon-carbon covalent bonds
• Carbonates, CO2, CO are not organic
• VSEPR theory carbon has 4 electron pairs
• A tetrahedral electron pair arrangement
• 4 covalent bonds, no lone pairs
• Tetrahedral molecular shape as well

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Hydrocarbons and alkanes

• Hydrocarbons contain only carbon and hydrogen
• Alkanes are hydrocarbons with only single bonds
  (no double or triple bonds)
• Saturated only single bonds
• Simplest alkane methane, CH4
• Ethane, molecular formula C2H6
• Structural formula (indicates connectivity) is
  CH3CH3

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Straight-chain alkanes (1 C through 4 C)

• Straight-chain (or normal) alkanes have carbons
  all attached in a row
• n- at beginning indicates straight-chain (normal)

Name Molecular formula Structural formula
Methane CH4 CH4
Ethane C2H6 CH3CH3
Propane C3H8 CH3CH2CH3
n-Butane C4H10 CH3(CH2)2CH3
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Straight-chain alkanes (5 C through 10 C)

• For straight-chain alkanes 5 C through 10 C, use
  Greek prefix followed by -ane

Name Molecular formula Structural formula
n-pentane C5H12 CH3(CH2)3CH3
n-hexane C6H14 CH3(CH2)4CH3
n-heptane C7H16 CH3(CH2)5CH3
n-octane C8H18 CH3(CH2)6CH3
n-nonane C9H20 CH3(CH2)7CH3
n-decane C10H22 CH3(CH2)8CH3
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Isomerism in alkanes

• n-Butane has an isomer (same number and kind
  atoms, different bonds)
• Same molecular formula, different structural
  formula
• Isobutane branched, all carbons not in a row
• CH3(CH3)CHCH3

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Isomerism in alkanes

• Iso- prefix means branched once
• Neo- prefix means branched twice
• n-Pentane, isopentane, neopentane
• More complex branched alkanes require different
  naming rules
• Any of the straight-chain alkanes can be made
  into substitutents - or branches off a main
  chain
• Methane becomes methyl as a branch (CH3)
• Ethane becomes ethyl as a branch (CH2CH3), etc

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Naming complex branched alkanes

• Start by identifying the longest carbon chain
• Identify branches off the longest chain as their
  substituent name (methyl, ethyl, propyl, etc)
• Number longest chain starting at end closest to
  the first branch
• Name the compound, starting with branches and
  indicating the number on the main chain to which
  the branch is attached

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Naming branched alkanes

• First identify longest chain (9 carbons)
• Number chain starting at end closest to a branch
• Identify branches by first numbering them (from
  main chain number)
• 2-methyl, 4-ethyl,
• 6-methyl
• Combine identical branches by saying 2,6-dimethyl
• Then give chain name
• 4-ethyl, 2,6-dimethyl nonane

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Alkenes and alkynes

• Alkenes hydrocarbons with carbon-carbon double
  bonds
• Alkynes hydrocarbons with carbon-carbon triple
  bonds
• Name by first finding longest carbon chain
• Chain name is same as alkane, but end is -ene for
  double bond, -yne for triple bond
• Start numbering on end closest to double/triple
  bond
• Location of multiple bond is given by the smaller
  numbered carbon involved in the bond

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Functional groups

• Most organic molecules are simply hydrocarbons
  with different groups of atoms attached
• Functional groups common groups of atoms found
  in organic molecules

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Common functional groups

• Alkyl halide X (where X is F, Cl, Br, or I)
• Alcohol OH
• Ether O
• Aldehyde
• Ketone

• Carboxylic acid
• Ester
• Amine NH2

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Alcohols

• Alcohols ROH
• Methanol CH3OH
• Starting material in synthesis of chemical
  products
• Racecar fuel
• Highly toxic, causes blindness
• Ethanol CH3CH2OH
• Formed by fermentation of glucose
• Important gasoline additive

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Carboxylic acids

• Carboxylic acid RCOOH
• Name by dropping e from parent hydrocarbon name,
  and adding oic acid
• CH3COOH ethanoic acid (acetic acid is common
  name)
• CH3CH2CH2CH2COOH pentanoic acid

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Esters

• Esters RCOOR
• Formed by reaction of carboxylic acid and alcohol
• RCOOH ROH ? RCOOR H2O
• Name by first using alcohol fragment as a
  fragment name
• Then add root of carboxylic acid followed by ate
• Ex. Acetic acid ethyl alcohol ? ethyl acetate