Dolbier HW Solutions 244

Dolbier HW Solutions 244 - ( c ) 1,3-Dibromopropane is made...

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( b ) Write the carbon skeleton corresponding to 2,2,6,6-tetramethylheptane. Compounds of molecular formula C 11 H 20 have two double bonds or one triple bond. The only compounds with the proper carbon skeleton are the alkyne and the allene shown. 10.20 The dienes that give 2,4-dimethylpentane on catalytic hydrogenation must have the same carbon skeleton as that alkane. 10.21 The important piece of information that allows us to complete the structure properly is that the ant repellent is an allenic substance. The allenic unit cannot be incorporated into the ring, because the three carbons must be collinear. The only possible constitution is therefore 10.22 ( a ) Allylic halogenation of propene with N -bromosuccinimide gives allyl bromide. ( b ) Electrophilic addition of bromine to the double bond of propene gives 1,2-dibromopropane.
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Unformatted text preview: ( c ) 1,3-Dibromopropane is made from allyl bromide from part ( a ) by free-radical addition of hydrogen bromide. H 2 C CHCH 2 Br Allyl bromide 1,3-Dibromopropane BrCH 2 CH 2 CH 2 Br HBr peroxides H 2 C CHCH 3 Propene 1,2-Dibromopropane BrCH 2 CHCH 3 Br 2 Br H 2 C CHCH 3 Propene Allyl bromide H 2 C CHCH 2 Br CCl 4 , heat N-bromosuccinimide C HO CHCCH 3 O CH 3 CH 3 HO CH 3 or or 2,4-Dimethyl-1,3-pentadiene conjugated diene ( a ) 2,4-Dimethyl-1,4-pentadiene isolated diene 2,4-Dimethyl-2,3-pentadiene cumulated diene ( c ) 2,4-Dimethylpentane ( b ) C H 2 Pt (CH 3 ) 3 CC CCH 2 C(CH 3 ) 3 (CH 3 ) 3 CCH CHC(CH 3 ) 3 C 2,2,6,6-Tetramethyl-3-heptyne 2,2,6,6-Tetramethyl-3,4-heptadiene 238 CONJUGATION IN ALKADIENES AND ALLYLIC SYSTEMS...
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