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 (300+ words):
In organic chemistry and biochemistry, reduction refers to the gain of electrons by a molecule, atom, or ion. When applied to organic compounds, reduction is typically characterized by changes in the number or type of bonds in a molecule. Specifically, two key indicators of reduction in organic molecules are:
- An increase in the number of carbon-hydrogen (C-H) bonds
- A decrease in the number of carbon-heteroatom bonds (C-Z bonds), where “Z” represents a more electronegative atom like oxygen, nitrogen, or halogens.
1. Increased Number of C-H Bonds
Reduction often involves the addition of hydrogen atoms to a compound. Since hydrogen has one electron, adding it can result in the molecule gaining electrons overall. In organic molecules, this typically leads to the formation of more C-H bonds, which is a hallmark of reduction. For instance:
- The reduction of an alkene to an alkane involves the addition of hydrogen across the double bond, creating two new C-H bonds.
- The reduction of a carbonyl group (C=O) to an alcohol (C-OH) also involves the addition of hydrogen, forming a new C-H bond on the carbon.
2. Fewer C-Z Bonds
Conversely, reduction often involves the removal of electronegative atoms or groups (like oxygen or halogens) bonded to carbon. These C-Z bonds are typically polar, with electrons being pulled toward the more electronegative atom. When these bonds are replaced by hydrogen (as in reductions), the molecule becomes less oxidized and more reduced.
For example:
- The reduction of a carboxylic acid (R-COOH) to a primary alcohol (R-CH2OH) results in the loss of two C-O bonds (C-Z bonds) and the gain of two C-H bonds.
Summary:
Thus, a compound is considered reduced when:
- It gains hydrogen atoms (increased C-H bonds)
- It loses electronegative atoms (fewer C-Z bonds)
This explains why the best answer is:
“Both increased number of C-H bonds and fewer C-Z bonds.”