Frequency (cm⁻¹)

Origin/Type of Vibration

Functional Group Assignment

3431/3423

Stretching vibration of O-H group in R-OH and Ph-OH

Thought to come from -O-H of PT/PTE polyphenols e.g., catechin.

2928/2926

2 bands. Stretching vibration of a -C-H (sp³) bond in alkyls

Supposedly from -C-H bonds

in the saturated parts of PT- catechin rings.

1629/1528

2 bands. Stretching of a -C=C- bond in a ring

Certainly from the unsaturated side rings of PT/PTE catechins. The conjugation is remarkably incomplete since it is absent in the middle ring, otherwise, there would have presented as 3 bands.

1377

Medium peak. In-plane bending of -OH

Attributable to in-plane-bending movement of -OH groups of PT catechin units. That due to the out-of-plane stretch was seen at 617 cm⁻¹.

1142

-C-H (Sp³) bending

Conceivably from the α-CH₂- bond of the partially saturated middle ring of PT catechins.

1160/1034

-C-O-C- stretchof a large cyclic ethers-i.e. alkoxy group

Likely from the -C-O- of the ether bearing middle ring of PT catechins.

823/668

C-H- stretch of aromatic and substituted aromatics.

Presumably from the aromatic

rings of PT catechins; ortho and para di-substituted aromatic rings