Answer:
2-chlorobutane.
Step-by-step explanation:
Hello,
In this case, the treatment of the substance A with sodium methoxide to yield trans-2-butene stands for a dehydrohalogenation in the presence of a strong base (the sodium methoxide), such chemical reaction is undergone by alkyl halides, in this case with chlorine, based on its molecular formula. In such a way, on the attached picture, you will find both the structure of the 2-chlorobutane and its chemical reaction to yield the trans-2-butene throughout the usage of sodium methoxide.
Best regards.