Final answer:
Methylamine (CH3NH2) is not effective for deprotonating a terminal alkyne because it is too weak of a base compared to stronger agents like NaH and amide anion (NH2-).
Step-by-step explanation:
The question asks which of the following bases is NOT effective for deprotonating a terminal alkyne. Among the given options, (d) CH3NH2, which is methylamine, is NOT an effective base for deprotonating a terminal alkyne. Terminal alkynes require strong bases due to their relatively weak acidity (pKa ~25), and while agents such as NaH and NH2- are sufficiently strong, methylamine is too weak to fully deprotonate a terminal alkyne. In contrast, (a) NaH and (c) NH2- are capable of deprotonating terminal alkynes due to their strong basicity, while (b) KOH is not typically strong enough to do so.