If a compound is reduced, what is the result?
Fewer C-H bonds
Increased number of C-H bonds
Fewer C-Z bonds
Both increased number of C-H bonds and fewer C-Z bonds
The Correct Answer and Explanation is:
Correct Answer:
Both increased number of C-H bonds and fewer C-Z bonds
Explanation
In organic chemistry, reduction refers to the gain of electrons by a molecule. Practically, this often involves an increase in hydrogen content or a decrease in the number of bonds to more electronegative atoms, such as oxygen, nitrogen, or halogens. These electronegative atoms are typically represented as Z in the general notation C–Z.
1. Increased Number of C–H Bonds:
When a compound is reduced, it often gains hydrogen atoms. For example, when an aldehyde is reduced to a primary alcohol, a hydrogen atom is added to the carbon and to the oxygen, increasing the number of C–H bonds. This hydrogenation increases the electron density around carbon and indicates reduction.
Example:
Aldehyde → Alcohol
R–CHO + H₂ → R–CH₂OH
In this reaction, the carbon in the aldehyde has one hydrogen, while the carbon in the alcohol has two. This is a reduction due to the increased number of C–H bonds.
2. Fewer C–Z Bonds (Where Z is More Electronegative than Carbon):
Reduction also involves the loss of bonds to electronegative atoms such as oxygen (O), nitrogen (N), halogens (Cl, Br, etc.), or sulfur (S). These atoms pull electron density away from carbon, so removing them increases electron density on the carbon—another hallmark of reduction.
Example:
Carboxylic acid → Alcohol
R–COOH + reducing agent → R–CH₂OH
Here, the carbon initially bonded to two oxygen atoms ends up bonded to just one oxygen and two hydrogens. The C–O (C–Z) bonds are reduced.
Conclusion:
Thus, a compound that undergoes reduction will generally show an increase in C–H bonds and a decrease in C–Z bonds, aligning with both criteria in the correct answer. This understanding is essential for interpreting redox reactions in organic and biological chemistry.
