The IR spectrum of 1,8-nonadiyne displays a strong, sharp band at 3300 cm^-1. What is the origin of this absorption? Treatment of 1,8-nonadiyne with NaNH₂, then with D₂O, leads to the incorporation of two deuterium atoms, leaving the molecule unchanged otherwise. The IR spectrum reveals that the peak at 3300 cm^-1 has disappeared, but a new one is present at 2580 cm^-1.

(a) What is the product of this reaction?

(b) What new bond is responsible for the IR absorption at 2580 cm^-1?

(c) Using Hooke’s law, calculate the approximate expected position of this new band from the structure of the original molecule and its IR spectrum. Assume that k and f have not changed.