LecturePLUS Timberlake 1

Haloalkanes, 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

H2C=CH2 ethene (ethylene)

H2C=CH-CH3 propene (propylene)

cyclohexene

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Alkynes

Carbon-carbon triple bonds Names end in -yne

HCCH ethyne(acetylene)

HCC-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

CH2=CHCH2CH3 1-butene

CH3CH=CHCH3 2-butene

CH3CHCHCH3 2-butyne

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Learning Check HA3

Write the IUPAC name for each of the following unsaturated compounds:

A. CH3CH2CCCH3

CH3

B. CH3C=CHCH3 C.

CH3

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Solutions HA3

Write the IUPAC name for each of the following unsaturated compounds:

A. CH3CH2CH=CHCH3 2-pentyne

CH3

B. CH3C=CHCH3 C.

2-methyl-2-butene 3-methylcyclopentene

CH3

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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

H–C=C–H + H2 H–C–C–H

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

CH2=CHCH2CH3 + H2

CH3CH2CH2CH3

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Adding Halogens

Halogens also add to the double bond of an alkene.

H2CCH2 + Cl2

H2C CH2

Cl Cl

CH3C CCH2CH3 + Br2 CH3C CCH2CH3

Br Br

Br Br

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Learning Check HA5

Write the product of the following addition reactions:

CH3CH=CHCH3 + H2

+ Br2

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Solution HA5

Write the product of the following addition reactions:

CH3CH=CHCH3 + H2 CH3CH2CH2CH3

+ Br2Br

Br

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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

CH3CH2CH2CH2CH2CH=CHCH2CH=CH(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 their total calories are 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

CH3CH2CH=CHCH2CH=CHCH2CH=CH(CH2)7COOH

eicosapentaenoic acid (EPA) 20 carbon atoms

CH3CH2(CH=CHCH2)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.