Question

The correct order of increasing bond length of $ C - H, C - O, C - C$ and $ C = C $ is

• A. $C-C < C = C< C-O < C-H$
• B. $C-O < C-H < C-C < C = C$
• C. $C-H < C - O < C-C < C = C$
• D. $C - H < C = C < C-O < C - C$

Answer 1

The Correct Option is D

To determine the correct order of increasing bond length among C - H, C - O, C - C, and C = C bonds, we need to consider the following concepts:

1. Bond Length and Bond Order: Generally, the bond length decreases as the bond order increases. A single bond has a longer bond length than a double bond, and a double bond is longer than a triple bond.
2. Electronegativity and Bond Type: The bond between atoms with different electronegativities (e.g., C - O) involves some ionic character, which can affect bond length.
3. Typical Bond Lengths:
   1. C - H: Typically around 1.09 Å.
   2. C = C (double bond): Typically around 1.34 Å.
   3. C - C (single bond): Typically around 1.54 Å.
   4. C - O: A single bond is slightly shorter than C - C due to extra s-character and some ionic character.

Now, let's analyze the bonds one by one to determine the order of increasing bond length:

1. C - H has the highest bond order and shortest bond length due to the large difference in electronegativity and s-character of hydrogen.
2. C = C bond, being a double bond, has shorter bond length than C - C but longer than C - H.
3. C - O bond typically involves more s-character in hybridized orbitals than C - C, making it shorter than C - C, but longer than C = C.
4. C - C (single bond) is longest compared to the others due to its lower bond order.

Thus, the order of increasing bond length is: C - H < C = C < C - O < C - C.