Question

Which of the following molecules has longest C-C bond length?

• A. Propyne
• B. Propene
• C. Propane
• D. All of these

Answer 1

The correct option is C Propane

• Propane has $s{p}^3$ hybridization. Propene has $s{p}^2$ hybridization while propyne has $sp$ hybridization.
  
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• The percentage '$s$' character in $s{p}^3$, $s{p}^2$ and $sp$ hybridized carbon atoms is 25%, 33.33% and 50% respectively.
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• More the percentage '$s$' character, more the electronegativity.
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• More the electronegativity, more the polarity of the bond. And the more polar bond is shorter and stronger.
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• Hence propane has the longest $C-C$ bond.
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Option C is correct.