Chapter 11 Haloalkanes, Alkenes, and Alkynes Geometric Isomers of Alkenes Addition Reactions Robert J. O'Reilly

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 Robert J. O'Reilly

Alkenes Carbon-carbon double bonds Names end in -ene H2C=CH2 ethene (ethylene) H2C=CH-CH3 propene (propylene) cyclohexene Robert J. O'Reilly

Alkynes Carbon-carbon triple bonds Names end in -yne HCCH ethyne(acetylene) HCC-CH3 propyne Robert J. O'Reilly

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 CH3CHCHCH3 2-butyne Robert J. O'Reilly

Learning Check HA3 Write the IUPAC name for each of the following unsaturated compounds: A. CH3CH2CCCH3 CH3 B. CH3C=CHCH3 C. Robert J. O'Reilly

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 Robert J. O'Reilly

Cis and Trans Isomers Double bond is fixed Cis/trans Isomers are possible CH3 CH3 CH3 CH = CH CH = CH cis trans CH3 Robert J. O'Reilly

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 Robert J. O'Reilly

Products of Hydrogenation Adding H2 to vegetable oils produces compounds with higher melting points Margarines Soft margarines Shortenings (solid) Robert J. O'Reilly

Learning Check HA4 What is the product of adding H2 (Ni catalyst) to 1-butene? Robert J. O'Reilly

Solution HA4 What is the product of adding H2 (Ni catalyst) to 1-butene? Ni CH2=CHCH2CH3 + H2 CH3CH2CH2CH3 Robert J. O'Reilly

Adding Halogens Halogens also add to the double bond of an alkene. H2CCH2 + Cl2 Robert J. O'Reilly

Learning Check HA5 Write the product of the following addition reactions: CH3CH=CHCH3 + H2 Robert J. O'Reilly

Solution HA5 Write the product of the following addition reactions: CH3CH=CHCH3 + H2 CH3CH2CH2CH3 Robert J. O'Reilly

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 Robert J. O'Reilly

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. Robert J. O'Reilly

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. Robert J. O'Reilly

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). Robert J. O'Reilly

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 Robert J. O'Reilly

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 Robert J. O'Reilly

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. Robert J. O'Reilly

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. Robert J. O'Reilly