How many sigma bonds are there in CH2 = CH - CH = CH2
Correct answer: B. 9
- A. 6
- B. 9
- C. 11
- D. 4
Explanation
The molecule CH2=CH-CH=CH2 consists of four carbon atoms and four hydrogen atoms. Each carbon atom forms single sigma bonds with hydrogen atoms:The first carbon (CH2) forms 2 sigma bonds with hydrogen.The second carbon (CH) forms 1 sigma bond with hydrogen.The third carbon (CH) forms 1 sigma bond with hydrogen.The fourth carbon (CH2) forms 2 sigma bonds with hydrogen.Additionally, each double bond consists of one sigma bond and one pi bond between adjacent carbon atoms:There are 3 carbon-carbon sigma bonds in the molecule (one for each pair of adjacent carbon atoms).Adding all the sigma bonds together, we have 2 + 1 + 1 + 2 (from C-H) + 3 (from C-C) = 9 sigma bonds in total.Options 6, 11, and 4 are incorrect because they either underestimate or overestimate the number of sigma bonds by not accurately accounting for all the bonds present in the molecule.
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About Sigma and Pi Bonds
A sigma bond forms by direct end-to-end overlap along the internuclear axis, whereas a pi bond forms by sideways overlap of parallel orbitals. The topic covers single, double and triple bonds, bond composition, restricted rotation and the relation between sigma and pi bonding and orbital hybridisation.
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