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 :
The correct answer is:
Both increased number of C-H bonds and fewer C-Z bonds.
Detailed Explanation (300+ words):
In chemistry, reduction refers to a process where a molecule gains electrons. In organic chemistry specifically, reduction usually involves increasing the number of carbon-hydrogen (C-H) bonds or decreasing the number of bonds between carbon and more electronegative atoms, such as oxygen (O), nitrogen (N), or halogens (Z represents a generic electronegative atom).
Let’s break it down:
- Increased number of C-H bonds:
When a compound is reduced, hydrogen atoms are often added to it. For example, when an alkene (a molecule with a carbon-carbon double bond) is reduced (such as by hydrogenation), it becomes an alkane (a molecule with more carbon-hydrogen bonds). This is because hydrogen atoms are added across the double bond, creating more C-H bonds. Thus, the number of C-H bonds increases during reduction. Example:
[
CH_2=CH_2 \quad (Ethene) \quad \xrightarrow{H_2} \quad CH_3-CH_3 \quad (Ethane)
] - Fewer C-Z bonds:
Reduction often removes bonds between carbon and electronegative atoms (Z), such as oxygen in carbonyl groups (C=O) or halides (C-X bonds where X = Cl, Br, I). Removing a bond to a more electronegative atom effectively adds electrons to the carbon, making it more reduced. Example:
Reduction of a carbonyl group (C=O) to an alcohol (C-OH) reduces the carbon because the double bond to oxygen (an electronegative atom) is broken and replaced with a C-H bond (in some reductions) or at least reduces the bond order (as in C-OH). [
R-CHO \quad (Aldehyde) \quad \xrightarrow{[H]} \quad R-CH_2OH \quad (Primary\ Alcohol)
]
Summary:
Reduction in organic compounds generally results in:
- More C-H bonds (more hydrogen added to carbon).
- Fewer C-Z bonds (less bonding to electronegative atoms like O, N, or halogens).
Both happen because adding hydrogen or removing bonds to electronegative elements effectively gives carbon more electron density, which is the essence of a “reduction” process.