Question

I need to compare the IR SPECTRA for benzophenone and triphenylmethanol. The image below is from the IR spectra of my product ( supposed triphenylmethanol) that i got at the experiment.

Answer 1

The IR spectrum of benzophenone is shown below:

The main distinguishing feature is the C=O stretching at 1660 cm-1 (peak 2).

The IR spectrum of triphenylmethanol is shown below:

The main distinguishing feature is the O-H stretching at 3470 cm-1 (peak 1).

The other peaks in both spectra are very similar due to the similar structural unit in benzophenone and triphenylmethanol. These include the aryl C-H stretching at 3060 cm-1, the aryl C=C ring stretching at 1440-1600 cm-1 and the aryl C-C and C-H bending modes below 1000 cm-1.

You should also consider the IR spectrum of the precursor to benzophenone: the alkyl benzoate ester starting material (methyl or ethyl benzoate?). The typical IR spectrum is shown below. The main distinguishing feature is the C=O stretching at 1726 cm-1.

Looking at the IR spectrum of your product, there is a very large C=O stretching peak evident at around 1750 cm-1. It is somewhat high compared to the C=O stretching in benzophenone (1660 cm-1) but is very close to the C=O stretching of alkyl benzoate ester (1726 cm-1). This suggests that there is a significant amount of the unreacted alkyl benzoate ester present in your product.

There is apparently also some benzophenone (C=O stretching peak at 1660 cm-1) and triphenylmethanol (O-H stretching peak at 3470 cm-1) present in your product.