Question

What features should I expect to see in a FTIR spectra of the polyester of Hydroquinone and Terephthaloyl Chloride?

I have included an image of the spectra as a prompt.

Thanks in advance! :)

FTIR Absorbance Spectra Procedure 3 Absorbance 500 1000 1500 2000 2500 3000 3500 4000 4500 Wavenumber (cm-1)

Answer 1

Polyesters have backbone of ester bonds (-O(CO)-) , this polyester is synthesised from aromatic acid chloride (Terephthaloyl Chloride ) and hydroquinone .

HOOC-Ar-COOH + HO-Ar-OH $\rightarrow$ -(O(CO)- Ar-(CO)O-Ar-)_n- + 2n H₂O

FT-IR spectra of this aromatic polyester should contain following features, thus The IR spectra should be  consistent with expected polymer structure:

• Phenolic (Ar-OH) peak should be absent or very weak : your spectra agrees.
• Carbonyl region : It must show peak corresponding to carbonyl of aromatic polyester unit ( it is present in given spectra ~1770-1790 cm-1 : strong peak) , which confirms ester backbone of resulting polymer, intense strong peak confirms extensive presence of ester linkages.
• Other bands of ester group corresponding to -C-C-O- stretch around ~1270-1290 cm-1 and 1100-1200 cm-1 for -O-C-C- stretch.
• Since, aromatic ring is 1,4-disubstituted a strong peak around ~800-830 (strong) should be observed, you can see -C-Cl peak in same region if reaction is not complete.