Experimental and Theoretical Investigations of Terahertz Spectra of the Structural Isomers: Mannose and Galactose

Table 4

Comparison of the absorption peaks between the experimental and best-fit calculated spectra and the mode descriptions of mannose and galactose.

Mannose
Mode	Exp.	Cal.	Mode description^a
a	0.91	0.94	80% ET along b-axis, 20% ER along c-axis
b	1.72		50% ET along a-axis, 50% ER along c-axis
c	1.99	2.11	60% ER along a-axis, 40% IM (CH2OH group wagging, hydroxyl groups torsions)
		2.31	85% ET along c-axis, 15% ER along a-axis
d	2.45	2.46	75% ED along c-axis, 25% ED along a-axis
		2.82	50% ET along c-axis, 25% ER along a-axis, 25% ER along b-axis.
e	3.08	2.93	60% ED along c-axis, 40% ET along a-axis
f	3.26	3.26	50% ED along c-axis, 50% IM (pyranose ring deformation, CH2OH group deformation.)
		3.39	55% ET along c-axis, 45% ER along a-axis
g	3.53	3.68	50% ED along a-axis, 50% IM (C4HOH group wagging, CH2OH deformation)
h	3.90	3.80	70% ED along b-axis, 30% ER along c-axis
Galactose
Mode	Exp.	Cal.	Mode description^a
		1.80	65% ER along a-axis, 35% ER along b-axis
i	2.14	2.06	55% ED along a-axis, 45% ER along c-axis
ii	2.32		60% ET along a-axis, 40% IM (C2 hydroxyl, C3 hydroxyl groups wagging)
iii	2.47	2.43	75% ER along a-axis, 25% ET along c-axis
		2.65	55% ER along b-axis, 45% ER along c-axis
iv	2.83	2.79	80% ET along a-axis, 20% ER along b-axis
v	3.08	2.94	40% ER along a-axis, 60% IM (pyranose ring deformation, CH2OH group wagging)
vi	3.37		60% ET along a-axis, 40% ER along b-axis
		3.70	75% ER along a-axis, 25% ER along c-axis
vii	3.92	3.81	70% ER along a-axis, 30% IM (pyranose ring torsion, CH2OH group wagging)

^aET: external translation; ER: external rotation; ED: external deformation; IM: internal motion.