Question

what stretching frequencies (in cm⁻¹) are present in the structure below?
none of these
1500
2950
3095
all of these

Explanation:

Step1: Identify bond types in structure

The structure is 1,2 - dimethylbenzene. It has C - H bonds of sp² - hybridized carbon (aromatic C - H) and sp³ - hybridized carbon (aliphatic C - H), and C - C bonds (aromatic and aliphatic).

Step2: Recall stretching - frequency ranges

• Aromatic C - H stretching occurs around 3020 - 3100 cm⁻¹.
• Aliphatic C - H (sp³) stretching occurs around 2850 - 3000 cm⁻¹.
• Aromatic C - C stretching occurs around 1450 - 1600 cm⁻¹.

Step3: Match frequencies to options

• 3095 cm⁻¹ is in the range of aromatic C - H stretching.
• 2950 cm⁻¹ is in the range of aliphatic C - H stretching.
• 1500 cm⁻¹ is in the range of aromatic C - C stretching.

Answer:

E. all of these