question_answer

The\[C-H\]bond distance is the longest in

A)  \[{{C}_{2}}{{H}_{2}}\]          

B)  \[{{C}_{2}}{{H}_{4}}\]

C)  \[{{C}_{2}}{{H}_{4}}B{{r}_{2}}\]       

D)  \[{{C}_{6}}{{H}_{6}}\]

Correct Answer: C

Solution :

 As the\[s-\]character or number of TC-electrons increases, bond length decreases. \[H-\underset{sp}{\mathop{C}}\,\overset{2\pi }{\mathop{\equiv }}\,\underset{sp}{\mathop{C}}\,H;\]        Therefore,\[{{C}_{2}}{{H}_{4}}B{{r}_{2}}\]due to the absence of \[\pi -\]electrons or due to the presence of lesser\[s-\]character (25%), has the longest\[C-H\]bond distance.