Final answer:
The reduction of a molecule involves the gain of hydrogen or the loss of oxygen. Among the provided molecules, neither exhibits an increased number of hydrogens or decreased oxygens compared to a more oxidized structure within the context given, and thus, there is no clearly reduced molecule in the listed options based on the provided information.
Step-by-step explanation:
The question asks which molecule is reduced. According to organic chemistry principles, a molecule is considered reduced when it gains hydrogen atoms or loses oxygen atoms. In the oxidation and reduction sequence provided, methane (CH4) is the most reduced form, and carbon dioxide (CO2) is the most oxidized form. Looking at the provided molecules:
- A) H3C-CH3 (Ethane): This molecule has only carbon to hydrogen bonds and no bonds to oxygen, indicating it is in a relatively reduced state.
- B) H2O: Water is not typically considered in terms of reduction or oxidation in organic chemistry.
- C) HOOC=COOH (Oxalic Acid): Here, the carbon atoms have double bonds with oxygen, which is a characteristic of an oxidized state.
- D) O=C=O (Carbon Dioxide): Carbon dioxide is the most oxidized form of carbon in the sequence.
None of the molecules listed appears to be more reduced than its corresponding alkane or alkene form. Thus, the answer is not explicitly given among the options. However, if we consider the sequence of oxidation states, molecules A (Ethane) and B (Water) have the fewest number of bonds to oxygen, which could be considered 'reduced' relative to the other molecules with more oxidized carbon atoms. If the question is about reduction from an unspecified starting point, without further information, definitive identification of the reduced molecule is not possible.