Question

Question 38 Which of the following exhibits a restricted rotation around the carbon-carbon bond? butane 1-propanol 2-butene

Answer 1

The correct answer is 2-butene The structures of cis -2-butene and trans 2-butene are as follows: H2C CH3 Z or cis isom er: If the groups which have higher priority are present on the same side of the double bond in alkene then the isomer has Z or cis configuration. (2Z)-but-2-ene E or trans isomer: If the groups which have higher priority are present on the opposite side of the double bond in alkene; then the isomer has E or trans configuration. Structure I is a cis isomer as both H atoms are present on the same side of the double bond Structure II is a trans isomer as both H atoms are present on the opposite side of the double bond H2C H3C -CH3 In the above structure; hydrogen atoms represented by white color line and blue color lines indicted methyl groups. I-Cis-isomer II-Trans-isom er Н.С. H CH3 (2E)-but-2-ene In the un-branched alkene; for example 2-butene free rotation is restricted due to present of C = C , double bond, which will cause fixed ordination of substituent's around double bond Therefore the molecules can be converted without disconnecting or breaking the bonds is not possible