Ask Questions, Get Answers

Want to ask us a question? Click here
Browse Questions
Home  >>  JEEMAIN and AIPMT  >>  Chemistry  >>  Hydrocarbons
0 votes

Which one of the following has the smallest heat of hydrogenation per mole?

$\begin{array}{1 1}(a)\;\text{1-butane}&(b)\;\text{Trans-2-butane}\\(c)\;\text{Cis-2-butane}&(d)\;\text{1,3-butadiene}\end{array}$

Can you answer this question?

1 Answer

0 votes
We know that higher stability,lower is the heat of hydrogenation.Butene-2 is more stable than butene-1 because the double bond present in butene-2 is in the centre of the molecule$(CH_3CH=CHCH_3)$.Moreover trans-2 butene is more stable than cis-2-butene and thus its (i.e) trans-2-butene,heat of hydrogenation per mole will be less.
Values of heats of hydrogenation are listed here:
Trans-2-butene is more stable than cis-2-butene because in trans-2-butene the bulky groups are far apart whereas in cis-2-butene the bulky groups are crowded together.Due to this cis-isomer has more vander walls strain than trans-isomer and thus cis-isomer is less stable.
Hence (b) is the correct answer.
answered Mar 20, 2014 by sreemathi.v

Related questions

Ask Question
student study plans
JEE MAIN, CBSE, AIPMT Mobile and Tablet App
The ultimate mobile app to help you crack your examinations
Get the Android App