Compare and contrast the molecular structures of alkanes, alkenes, and alkynes. Include: trends in melting points and boiling points Name, draw, and construct molecular models of alkenes and alkynes Include: branched alkenes and alkynes Outline the transformation of alkanes to alkenes or alkynes and vice versa. Include: dehydrogenation/hydrogenation Additional KEY Terms unsaturated

Alkenes and Alkynes Contain C-C double and triple bonds General alkene formula C n H 2n General alkyne formula C n H 2n-2 More reactive than alkanes Known as unsaturated hydrocarbons CC H H HH

Thermal cracking: Process of breaking the long chain-alkanes found in petroleum into shorter chain alkanes and alkenes. Multiple bonds are also formed by removing a hydrogen chemically – dehydrogenation. C H H H + H 2 H HH C H H HH H H H + H 2 H C H H

Alkenes / Alkynes are converted to alkanes by hydrogenation or addition reaction.

Find parent chain with the double/triple bond. Named as total carbons using ending ene / yne Show the location of the bond by the carbon number separated with a hyphen. (2-pentene) Number carbons from the end that gives the lowest number to the double or triple bond. Name alkyl branches as done previously. Naming Alkenes and Alkynes

ethene CH 2 = CH 2 C = C H HH H ethyne CH ≡ CH C ≡ C H H C C H H HH C C H H

2-hexeneCH 3 CH=CHCH 2 CH 2 CH 3 3-hexyneCH 3 CH 2 C≡CCH 2 CH 3 C - C - C - C C - C = C ≡ C - C - C C

4-methyl-2-pentene (4-methylpent-2-ene) (Note, lowest number goes to the double bond)

CH 3 CH 2 CH(CH 3 )CH=C(C 2 H 5 )CH 2 CH 3 3-ethyl-5-methyl-3-heptene *Show double/triple bond in condensed formula.

Draw the structural formula for 1-butene. CH 2 =CH–CH 2 –CH 3 Draw a condensed for 2,5,5-trimethyl-2-hexene. CH 3 C(CH 3 )=CHCH 2 C(CH 3 ) 2 CH

HC≡CCH 2 C(C 2 H 5 ) 2 CH 2 CH(CH 3 )CH(CH 3 )CH 3 4,4-diethyl-6,7-dimethyl-1-octyne

Draw a structural of 2,2,5,5-tetramethyl-3-hexyne.

Like Alkyl groups (trimethyl), prefixes and numbers must be used to indicate multiple double or triple bonds. C = C – C = C1,3-butadiene 3-methyl-1,4-pentadiyne C ≡ C – C – C ≡ C C

Alkenes: C=C, C n H 2n, –ene. Alkynes: C≡C, C n H 2n-2,–yne. Parent chain is numbered to give the double or triple bond the lowest number. Draw the parent chain hydrocarbon with the double or triple bonds first. Add in alkyl groups and then hydrogen so each carbon has 4 bonds.

CAN YOU / HAVE YOU? Compare and contrast the molecular structures of alkanes, alkenes, and alkynes. Include: trends in melting points and boiling points Name, draw, and construct molecular models of alkenes and alkynes Include: branched alkenes and alkynes Outline the transformation of alkanes to alkenes or alkynes and vice versa. Include: dehydrogenation/hydrogenation Additional KEY Terms unsaturated