Quantum Mechanical Study on the Structure and Vibrational Spectra of Cyclobutanone and 1,2-Cyclobutanedione

Table 6

Comparative study of calculated wave numbers IR intensity and Raman intensity of 1,2-cyclobutanedione and cyclobutanone.

S. no.	Cyclobutanone				Cyclobutane 1,2-dione
	[B3PW91/6-31G (d, p)]				[B3PW91/6-31G (d, p)]
	Sc. freq.	IR int.	Raman activity	Assignments	Sc. freq.	IR int.	Raman activity	Assignments
1	42	4.11	0.33	O.O.P. ring bending	82	0.00	0.04	Ring twist
2	401	0.79	2.73	𝛾(C–C=O)	281	9.91	1.17	Ra(CH2)
3	462	3.15	4.25	𝛽(C–C=O)	284	3.04	3.79	Assy(C–C=O) Bending
4	623	0.00	0.01	R(CH2)	492	1.72	1.11	Symm(C–C=O) Bending
5	678	1.78	5.02	Ring deformation	525	0.00	0.12	Assy(C–C=O) Bending + 𝜔(CH2)
6	743	5.35	0.98	R(CH2)	695	8.77	0.03	𝜔(C–C=O)
7	819	1.22	3.50	Ring deformation	710	0.02	13.62	Ring deformation
8	912	0.34	10.67	Ring deformation	715	14.04	4.52	Ring deformation
9	920	0.16	1.82	𝜏(CH2)	923	17.82	9.59	Ring deformation
10	950	2.09	19.67	Ring deformation	934	0.18	6.77	𝜔(CH2) + 𝜔(C–C=O)
11	1057	0.76	0.14	Ring deformation	941	46.62	2.44	Rs(CH2)
12	1060	93.41	0.09	R(CH2)	994	0.01	0.01	𝜔(CH2)
13	1150	3.96	4.18	𝜔(CH2)	1030	113.97	5.36	Ring deformation
14	1179	0.32	13.69	𝜏(CH2)	1162	0.35	3.23	𝜈(C–C) + Ring breathing
15	1183	0.85	7.73	𝜏(CH2)	1166	0.00	0.88	𝛽(CH)
16	1201	5.46	0.63	𝜔(CH2)	1186	0.00	0.61	Ra(CH2)
17	1232	9.55	0.12	𝜔(CH2)	1380	4.44	14.64	𝛾(CH) + Ra(CH2)
18	1380	17.91	1.04	𝛿(CH2)	1401	21.5	11.38	S(CH2) + 𝛽(CH)
19	1394	1.23	29.08	𝛿(CH2)	1810	237.45	84.26	𝜈(C=O)
20	1449	0.85	9.37	𝛿(CH2)	1852	118.39	56.88	𝜈(C=O)
21	1837	277.65	10.79	𝜈(C=O)	2974	6.84	83.45	𝜈 s(CH)
22	2964	12.36	4.03	𝜈 s(CH2)	2980	0.13	74.57	𝜈 s(CH)
23	2968	8.31	189.8	𝜈 s(CH2)	3025	0.00	67.84	𝜈 as(CH2)
24	2990	23.03	124.08	𝜈 s(CH2)	3037	4.30	72.59	𝜈 as(CH2)
25	3017	3.68	19.04	𝜈 a(CH2)
26	3022	1.19	136.71	𝜈 a(CH2)
27	3047	23.07	58.28	𝜈 a(CH2)

𝜈: Stretching; 𝜈_s: symmetric stretching; 𝜈_as: asymmetric stretching; 𝛽: in-plane bending; 𝛾: out-of-plane bending; 𝜔: wagging; 𝜏: torsion; int: intensity.