In most organic chemistry textbooks, double bond cis/trans isomerism is exemplified by alkenes. It is also observed in cycloalkenes such as cyclooctene that can exist as either cis (a) or trans (b) isomer:
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(a) | (b) |
- (Z)-cyclooctene (PIN)
cis-cyclooctene
- (E)-cyclooctene (PIN)
trans-cyclooctene
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To the trans isomer, there is a twist — and the pun is fully intended. Have a look at the structures (c) and (d) (or at their 3-D models here, Fig. 2 and Fig. 3, respectively).
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(c) | (d) |
- (1E,1P)-cyclooct-1-ene (PIN)
(E,P)-cyclooctene
(E,Rp)-cyclooctene
- (1E,1M)-cyclooct-1-ene (PIN)
(E,M)-cyclooctene
(E,Sp)-cyclooctene
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