Chapter 11 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 H 2 C=CH 2 eth ene (ethyl ene ) H 2 C=CH-CH 3 prop ene (propyl ene ) cyclohex ene

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Alkynes



Carbon-carbon triple bonds



Names end in yne HC



CH eth yne (acet ylene ) HC



C-CH 3 prop yne

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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 CH 2 =CHCH 2 CH 3 1-butene CH 3 CH=CHCH 3 CH 3 CH



CHCH 3 2-butene 2-butyne

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Learning Check HA3

A.

Write the IUPAC name for each of the following unsaturated compounds: CH 3 CH 2 C



CCH 3 CH 3 CH 3 B. CH 3 C=CHCH 3 C.

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Solutions HA3

A.

Write the IUPAC name for each of the following unsaturated compounds: CH 3 CH 2 CH=CHCH 3 2-pentyne CH 3 CH 3 B. CH 3 C=CHCH 3 C. 2-methyl-2-butene 3-methylcyclopentene

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Cis and Trans Isomers



Double bond is fixed



Cis/trans Isomers are possible CH 3 CH = CH

cis

CH 3 CH 3 CH = CH

trans

CH 3

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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 + H 2 H – C – C – H H H ethene ethane

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Products of Hydrogenation

Adding H 2 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 H 2 catalyst) to 1-butene?

(Ni

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Solution HA4

What is the product of adding H 2 catalyst) to 1-butene?

(Ni Ni CH 2 =CHCH 2 CH 3 + H 2 CH 3 CH 2 CH 2 CH 3

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Adding Halogens

Halogens also add to the double bond of an alkene.

H 2 C



CH 2 + Cl 2 CH 3 C CCH 2 CH 3 + 2 Cl Cl H 2 C CH 2 Br Br CH 3 C CCH 2 CH 3 Br Br

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Learning Check HA5

Write the product of the following addition reactions:

CH 3 CH=CHCH 3 + H 2 + Br 2

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Solution HA5

Write the product of the following addition reactions: CH 3 CH=CHCH 3 + Br 2 + H 2

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CH 3 CH 2 CH 2 CH 3 Br 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 CH 3 CH 2 CH 2 CH 2 CH 2 CH=CHCH 2 CH=CH(CH 2 ) 7 COOH 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 CH 3 CH 2 CH=CHCH 2 CH=CHCH 2 CH=CH(CH 2 ) 7 COOH

 

eicosapentaenoic acid (EPA) 20 carbon atoms CH 3 CH 2 (CH=CHCH 2 ) 5 (CH 2 ) 2 COOH

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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.

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