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.”
Explanation:
Reduction in chemistry refers to the process where a compound gains electrons, and often, the addition of hydrogen (H₂) or the removal of oxygen occurs. This reaction leads to a decrease in the oxidation state of the atoms involved, especially carbon in organic molecules.
- Increased Number of C-H Bonds:
- During reduction, compounds often gain hydrogen atoms. In organic compounds, carbon is frequently bonded to oxygen, nitrogen, or other electronegative elements (denoted as C-Z bonds, where Z represents an atom such as O, N, or a halogen). When the compound is reduced, it typically reacts with hydrogen (H₂), leading to the addition of C-H bonds. This is especially common in reactions such as hydrogenation, where a carbon-carbon double bond (C=C) or a carbon-oxygen double bond (C=O) is broken, and the carbons gain hydrogen atoms.
- For example, in the reduction of an aldehyde (R-CHO) to a primary alcohol (R-CH₂OH), the C=O double bond is broken, and two C-H bonds are formed in its place.
- Fewer C-Z Bonds:
- Reduction also leads to the decrease in bonds between carbon and more electronegative atoms such as oxygen, nitrogen, or halogens. For example, when an aldehyde (R-CHO) is reduced to an alcohol (R-CH₂OH), the carbon-oxygen (C=O) double bond is reduced (converted to a single bond), removing the more electronegative element (oxygen) from the bond. Similarly, halogenated compounds (R-X, where X is a halogen) can undergo reduction reactions to remove the halogen atom and replace it with a hydrogen atom.
Thus, during reduction, the compound becomes more saturated with hydrogen atoms, increasing the number of C-H bonds and decreasing the number of C-Z bonds, such as C-O, C-N, or C-X bonds.