IMAT 2013 Q48 [Carbon to Carbon Bonds]

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Which of the following are correct about carbon to carbon bonds?

  1. The length of carbon to carbon bonds increases in the order C≡C, C=C, C­C.
  2. The strength of the C=C bond is less than twice the strength of the C­C bond.
  3. The carbon atoms are joined by six electrons in the C≡C bond.

A. 2 and 3 only
B. 1 and 3 only
C. 1, 2 and 3
D. 1 and 2 only
E. 3 only

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Let’s review each statement:

The first statement is correct, the highest electrostatic forces should be between the carbon’s nucleus to closer bonding electrons, which makes it shorter. Therefore, a simple carbon carbon bond should be the shortest and the longest should be one in which the electrons comes farther away from the nucleus.

The second statement is also correct, because even though it sounds as though it should be twice as strong- remember there is a slight electron repulsion in the double bond, and more repulsion from the nucleus. This makes the strength not accurately twice as strong, just slightly less.

The third statement is the most easily recognizable- a triple carbon, carbon bond should have 6 electrons shared. So, 3 is correct.

Our answer is therefore, C.