Chapter 11 Haloalkanes, Alkenes, and Alkynes

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Chapter 11Haloalkanes, Alkenes, and Alkynes

• Alkenes and Alkynes
• Geometric Isomers of Alkenes
• Addition Reactions

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Saturated and Unsaturated Compounds

• Saturated compounds (alkanes) have the maximum
  number of hydrogen atoms attached to each carbon
  atom
• Unsaturated compounds have fewer hydrogen atoms
  attached to the carbon chain than alkanes
• Unsaturated compounds contain double or triple
  bonds

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Alkenes

• Carbon-carbon double bonds
• Names end in -ene
• H2CCH2 ethene (ethylene)
• H2CCH-CH3 propene (propylene)
• cyclohexene

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Alkynes

• Carbon-carbon triple bonds
• Names end in -yne
• HC?CH ethyne(acetylene)
• HC?C-CH3 propyne

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Naming Alkenes and Alkynes

• When the carbon chain has 4 or more C atoms,
  number the chain to give the lowest number to
  the double or triple bond.
• 1 2 3 4
• CH2CHCH2CH3 1-butene
• CH3CHCHCH3 2-butene
• CH3CH?CHCH3 2-butyne

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Learning Check HA3

• Write the IUPAC name for each of the following
  unsaturated compounds
• A. CH3CH2C?CCH3
• CH3
• B. CH3CCHCH3 C.

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Solutions HA3

• Write the IUPAC name for each of the following
  unsaturated compounds
• A. CH3CH2CHCHCH3 2-pentyne
• CH3
• B. CH3CCHCH3 C.
• 2-methyl-2-butene
  3-methylcyclopentene

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Cis and Trans Isomers

• Double bond is fixed
• Cis/trans Isomers are possible
• CH3 CH3 CH3
• CH CH CH CH
• cis trans CH3

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Hydrogenation

• Adds a hydrogen atom to each carbon atom of a
  double bond
• H H H H
• Ni
• HCCH H2 HCCH
• H H
• ethene ethane

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Products of Hydrogenation

• Adding H2 to vegetable oils produces compounds
  with higher melting points
• Margarines
• Soft margarines
• Shortenings (solid)

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Learning Check HA4

• What is the product of adding H2 (Ni catalyst)
  to 1-butene?

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Solution HA4

• What is the product of adding H2 (Ni catalyst)
  to 1-butene?
• Ni
• CH2CHCH2CH3 H2
• CH3CH2CH2CH3

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Adding Halogens

• Halogens also add to the double bond of an
  alkene.
• H2C?CH2 Cl2

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Learning Check HA5

• Write the product of the following addition
  reactions
• CH3CHCHCH3 H2

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Solution HA5

• Write the product of the following addition
  reactions
• CH3CHCHCH3 H2 CH3CH2CH2CH3

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Unsaturated Fatty Acids

• Fatty acids in vegetable oils are omega-6 acids
  (the first double bond occurs at carbon 6
  counting from the methyl group)
• A common omega-6 acid is linoleic acid
• CH3CH2CH2CH2CH2CHCHCH2CHCH(CH2)7COOH
• 6
• linoleic acid, a fatty acid

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Trans Fats

• In vegetable oils, the unsaturated fats usually
  contain cis double bonds.
• During hydrogenation, some cis double bonds are
  converted to trans double bonds (more stable)
  causing a change in the fatty acid structure
• If a label states partially or fully
  hydrogenated, the fats contain trans fatty
  acids.

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Trans Fats

• In the US, it is estimated that 2-4 of our total
  Calories is in the form of trans fatty acid.
• trans fatty acids behave like saturated fatty
  acids in the body.
• Several studies reported that trans fatty acids
  raise LDL-cholesterol. Some studies also report
  that trans fatty acid lower HDL-cholesterol
• The trans fatty acids controversy will continue
  to be debated.

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Fats and Atheroschlerosis

• Inuit people of Alaska have a high fat diet and
  high blood cholesterol levels, but a very low
  occurrence of atherosclerosis and heart attacks.
• Fat in the Intuit diet was primarily from fish
  such as salmon, tuna and herring rather than from
  land animals (as in the American diet).

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Omega-3 Fatty Acids

• Fatty acids in the fish oils are mostly the
  omega-3 type (first double bond occurs at the
  third carbon counting from the methyl group).
• linolenic acid 18 carbon atoms
• CH3CH2CHCHCH2CHCHCH2CHCH(CH2)7COOH
• ?
• eicosapentaenoic acid (EPA) 20 carbon atoms
  CH3CH2(CHCHCH2)5(CH2)2COOH

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Atherosclerosis

• Plaques of cholesterol adhere to the walls of the
  blood vessels
• Blood pressure rises as blood squeezes through
  smaller blood vessels
• Blood clots may form
• Omega-3 fatty acids decrease the sticking of
  blood platelets (fewer blood clots)
• Omega-3 fatty acids can increase bleeding time

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Learning Check HA6

• (1) Ture or (2) False
• A. ____ There are more unsaturated fats in
  vegetable oils.
• B. ____ Vegetable oils have more omega-3 oils
  than found in fish.
• C. ____ Hydrogenation of oils converts some
  cis-double bonds to trans- double bonds.
• D. ____ Animal fats have more saturated fats.

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Solution HA6

• (1) True or (2) False
• A. _T__ There are more unsaturated fats in
  vegetable oils.
• B. _F__ Vegetable oils have more omega-3 oils
  than found in fish.
• C. _T__ Hydrogenation of oils converts some
  cis-double bonds to trans- double bonds.
• D. _T__ Animal fats have more saturated fats.