In order to explain the importance of the antiperiplanar proton, let’s consider a love story analogy. In this story, we have a bride who must choose between two suitors – protons A and B. The base represents the young lady’s parents, while the reaction conditions signify the circumstances under which the decision is made.
The first scenario takes place at room temperature (20°C) for 24 hours. This reaction is considered thermodynamic because it occurs over a long period of time and under specific temperature constraints. In this case, proton B is anti-periplanar to the bromine, while proton A is not. The bulky T-butoxide base cannot pick proton B due to its orientation, so it grabs proton A instead, forming an undesirable compound on the left.
In the second scenario, we introduce a more demanding condition with lower temperatures (0°C) and shorter reaction times (20 minutes). This reaction is under Huffman conditions or kinetic control since the process must happen quickly. In this case, both proton HA and proton HB are down or dash, making them opposite to the bromine leaving group. However, due to its size and orientation, the bulky T-butoxide base grabs proton HB, which is anti-periplanar and least hindered compared to proton HA.
As a result, the bride forms her desired compound on the right, leading to a happy marriage and a joyful wedding night. The story demonstrates how the antiperiplanar proton plays a crucial role in determining the outcome of certain organic reactions under different conditions. This concept helps chemists predict reaction pathways and improve their understanding of molecular structures and reactivity.
