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 a process in which a molecule gains electrons. This often translates structurally into either an increase in carbon-hydrogen (C–H) bonds or a decrease in carbon-heteroatom bonds (C–Z), where Z is typically a more electronegative atom such as oxygen, nitrogen, or a halogen.
1. Increased number of C–H bonds:
When a compound is reduced, it often gains hydrogen atoms. In organic molecules, this means more hydrogen atoms become bonded to carbon, increasing the number of C–H bonds. For example, the reduction of a carbonyl group (C=O) in an aldehyde or ketone to an alcohol adds hydrogen and converts the double bond to a single bond with an added hydrogen on the carbon. This is commonly seen in the reduction of aldehydes to primary alcohols or ketones to secondary alcohols using reducing agents like NaBH₄ or LiAlH₄.
2. Fewer C–Z bonds:
At the same time, reduction can also involve the removal of bonds between carbon and electronegative atoms. These C–Z bonds are usually polar due to the difference in electronegativity, making them susceptible to reduction. For instance, the reduction of a nitro group (–NO₂) to an amine (–NH₂) involves breaking N–O bonds. Similarly, the dehalogenation of an alkyl halide (removal of a halogen) reduces the number of C–Z bonds.
Conclusion:
Therefore, a reduction process in organic chemistry typically results in both an increase in C–H bonds and a decrease in C–Z bonds. Recognizing these changes is key to identifying whether a reaction is oxidative or reductive. That’s why “Both increased number of C-H bonds and fewer C-Z bonds” is the correct answer.
