Organic Spectroscopy

Step 1: Understanding NMR Signals.
In H-NMR, the number of signals corresponds to the number of distinct types of hydrogen atoms, and in C-NMR, it corresponds to the number of distinct carbon atoms.

Step 2: Analysis of Options.
- (1) 1,2,3,5-Tetramethylbenzene: This compound has four different methyl groups, leading to multiple signals.
- (2) 1,4-Diethylbenzene: This compound has two different ethyl groups, resulting in multiple H-NMR and C-NMR signals.
- (3) 1,2,4,5-Tetramethylbenzene: This compound has two types of hydrogen atoms and three types of carbon atoms, leading to exactly two H-NMR and three C-NMR signals. Hence, this is the correct option.
- (4) 1,2-Diethylbenzene: This compound results in more than two H-NMR signals due to the different positioning of the ethyl groups.

Step 3: Conclusion.
Thus, the correct answer is (3) 1,2,4,5-Tetramethylbenzene.

Final Answer:

Step 1: IR Absorption Bands.
- A sharp band around 2150 cm is characteristic of a C≡C stretch (alkyne), while a broad band around 3300 cm is characteristic of an N-H stretch (amines).

Step 2: Analysis of Options.
- (1) Alkyne ( ) shows the sharp band at 2150 cm and a stretch at 3300 cm due to the C-H stretch. This matches the given conditions.
- (2) Alkene ( ) would show a different stretch and does not match both bands.
- (3) Amines ( ) show a broad stretch near 3300 cm but not the 2150 cm band.
- (4) Amine ( ) would only show a broad N-H stretch without the C≡C stretch.

Step 3: Conclusion.
Thus, the correct answer is (1) Alkyne ( ).

Final Answer: