In the context of organic chemistry, which of the following statements best describes the energy transfer in a chemical reaction involving organic compounds?

• A. Energy is lost only when the reaction is $\mathrm{endothermic}$.
• B. Energy is completely conserved and no energy is lost.
• C. Energy is gained at each step of the reaction.
• D. Energy is lost primarily as $\mathrm{heat}$ during the reaction.

Answer: (D)

Verified step by step guidance

1. Understand that chemical reactions involve the breaking and forming of chemical bonds, which requires and releases energy, respectively.
2. Recognize that in any chemical reaction, energy is neither created nor destroyed, according to the law of conservation of energy. However, energy can be transferred between the system and its surroundings.
3. Identify that in exothermic reactions, energy is released to the surroundings, often in the form of heat, as the products have lower energy than the reactants.
4. Acknowledge that in endothermic reactions, energy is absorbed from the surroundings, as the products have higher energy than the reactants.
5. Conclude that in most chemical reactions involving organic compounds, some energy is lost to the surroundings as heat, which is a common form of energy transfer in these processes.