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Unformatted text preview: 7 -3 5 ~~
trans, trans cis,trans (a) ( b) ;=\'
cis,cis 2£,4£ 2Z,4£ 2£,4Z 2Z,4Z This problem is i ntended to show the difficulty of using cis-trans nomenclature with any but the simplest alkenes. Cis and trans are ambi guous: the first alkene in part ( a) is cis if the two similar substituents are considered, but trans if the chain is considered. The £-Z nomenc l ature i s unambiguous and i s preferred for a l l four o f these i somers. 7-36 (a) and (d) have no geometric i somers (b) trans-pent-2-ene (E)-pent-2-ene cis-pent-2-ene (Z)-pent-2-ene (c) �
trans-hex -3-ene (E)-hex -3-ene cis-hcx-3-ene (Z)-hex-3-ene (e) (f) y
Br Br trans- 1 ,2-dibromopropene (E)- 1 ,2-di bromopropene � B r cis- 1 ,2-dibromopropene 1(Z)- 1 ,2-dibromopropene
Br trans,trans-hexa-2 ,4-diene (2£,4E)-hexa-2,4-diene cis,trans-hexa-2,4-diene (2Z,4E)-hexa-2,4-diene cis,cis-hexa-2,4-diene (2Z,4Z)-hexa-2 ,4-diene 7-37 F (a) 1 H >===< F H H F H d i pole moment >===< F (b)
= Br 0 H >===< 1 Br Br H C H3 >===< CH3 Br dipole moment = 0 (c) Br Cl 1 Cl A Cl 1 Cl
H H l arger dipole moment (no bromines opposing the dipole of the chlorines) ( b) m aj or Br >===< 7-3 8 ( a) o +�
15 1 ( c) minor major mi nor ...
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This note was uploaded on 02/27/2010 for the course CHEM 140 taught by Professor Wade during the Spring '10 term at Whitman.
- Spring '10