Final answer:
The correct answer is option c. The reaction between sodium and ammonia produces an achiral trans alkene, as it favors the formation of the thermodynamically more stable trans product without any stereocenters.
Step-by-step explanation:
The major product of the reaction between sodium (Na) and ammonia (NH₃) is c) one achiral trans alkene. This type of reaction is typical of birch reductions, which are known to reduce aromatic rings to achiral trans alkenes. In the context of stereochemistry, the resulting trans alkene is achiral because it has a plane of symmetry and does not have non-superimposable mirror images, hence it cannot exist as enantiomers.
The reaction under consideration does not involve any chiral reactants or catalysts that would lead to the formation of enantiomerically enriched products. Therefore, the production of a racemic mixture or a chiral product is not expected. Instead, the reaction favors the formation of the thermodynamically more stable trans alkene product without any stereocenters, leading to an achiral molecule.