DFT CALCULATION AND RAMAN SPECTROSCOPY STUDIES OF α-LINOLENIC ACID

Peng, Heng; Hou, Hua-Yi; Chen, Xiang-Bai

doi:10.21577/0100-4042.20170749

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Artigo • Quim. Nova 44 (08) • 2021 • https://doi.org/10.21577/0100-4042.20170749 copy

DFT CALCULATION AND RAMAN SPECTROSCOPY STUDIES OF α-LINOLENIC ACID

Authorship SCIMAGO INSTITUTIONS RANKINGS

Density functional theory (DFT) calculation and Raman scattering experiment have been applied to investigate an important essential fatty acid, α-linolenic acid (ALA). The DFT calculation was performed with geometry optimization and harmonic vibration using B3LYP functions with polarized 6-311+G(d,p) basis. The DFT calculated vibrational modes of ALA molecule are in excellent agreement with the Raman experimental results. A complete vibrational modes assignment is provided on the basis of potential energy distribution calculation. In addition, the DFT calculation and Raman experiment indicate that the relative intensity ratio of two characteristic modes at 1660 cm^-1 and 1440 cm^-1 is correlated with the number of C=C double bond in the acid chain, which may provide a simple and convenient method to differentiate ALA with other types of unsaturated fatty acids. Furthermore, the Mulliken atomic charge distribution and frontier molecular orbitals of ALA molecule were calculated.

Keywords:
α-Linolenic acid; DFT calculation; Raman spectroscopy; atomic charge distribution; frontier molecular orbital

Bond	Cal. length (Å)	Bond	Cal. angle (°)
O1-C11	1.3588	C4-C3-C5	113.4897
O1-H	0.9692	C3-C4-C6	113.2847
O2=C11	1.2057	C3-C5-C7	113.0784
C3-C4	1.5328	C4-C6-C8	114.0404
C3-C5	1.5328	C5-C7-C9	113.7715
C4-C6	1.5325	C6-C8-C10	113.2579
C5-C7	1.5335	C7-C9-C11	114.0322
C6-C8	1.5418	O1-C11-O2	122.0911
C7-C9	1.5309	O1-C11-C9	111.4637
C8-C10	1.505	O2-C11-C9	126.4283
C9-C11	1.5118	C10=C12-13	128.0164
C10=C12	1.3356	C4-C3-C5	113.4897
C12-C13	1.5102	C3-C4-C6	113.2847
C13-C14	1.5099	C12-C13-C14	112.0295
C14=C15	1.3356	C13-C14=C15	128.0647
C15-C16	1.5105	C14=C15-C16	128.0182
C16-C17	1.511	C15-C16-C17	111.7379
C17=C18	1.3365	C16-C17=C18	127.9366
C18-C19	1.5043	C17=C18-C19	128.4104
C19-C20	1.5382	C18-C19-C20	112.5096

Exp.	Cal.		Assignment(%PED)
Exp.	Scaled	Unscaled	Assignment(%PED)
	92	91	τ(C11C9C7C5)(20)+τ(C4C6C8C10)(25)+τ(C9C7C5C3)(14)
	105	104	β(C3C4C6)(18)+β(C5C3C4)(16)+β(C7C5C3)(13)+τ(C11C9C7C5)(17)
	123	122	τ(C5C3C4C6)(18)
142v	143	142	β(C17C16C15)(16)+τ(C7C5C3C4)(15)
154vw	151	150	τ(C4C6C8C10)(12)+τ(C5C3C4C6)(26)+τ(C7C5C3C4)(11)
182vw	179	178	β(C15=C14C13)(11)+β(C18=C17C11)(16)+β(C19C18=C17)(16)+β(C16C15=C14)(17)
	215	214	β(C12=C10C8)(15)+β(C13C12=C10)(12)+β(C4C6C8)(11)+β(C7C5C3)(10)
228vw	226	225	β(C14C13C12)(19)+β(C20C19C18)(14)+τ(C19C18=C17C16)(13)
	232	231	β(C11C9C7)(18)+β(C9C7C5)(15)
	241	240	τ(H₃C20C19C18)(49)
	263.	262	β(C12=C10C8)(14)+β(C13C12=C10)(17)+β(C4C6C8)(10)
274vw	275	274	β(O1C11C9)(21)+β(C11C9C7)(18)+β(C3C4C6)(12)
	307	306	β(C6C8C10)(13)+β(C20C19C18)(12)+τ(C13C12=C10C8)(10)
330vw	336	335	β(C15=C14C13)(19)+β(C18=C17C16)(18)+β(C19C18=C17)(16)+β(C16C15=C14)(12)
	345	344	β(C14C13C12)(13)+β(C17C16C15)(14)+β(C6C8C10)(11)+β(C20C19C18)(16)
396w	407	406	β(O1C11C9)(12)+β(C3C4C6)(10)+β(C5C3C4)(26)+β(C9C7C5)(15)
424vw	423	422	β(C4C6C8)(14)+τ(C13C12=C10C8)(12)
462vw	459	458	β(C20C19C18)(10)+τ(C16C15=C14C13)(17)
494vw	496	496	β(C12=C10C8)(11)+τ(C13C12=C10C8)(12)
517vw	521	521	τ(HO1C11C9)(11)+τ(C19C18=C17C16)(11)
	522	522	τ(HO1C11C9)(27)+o(O2C9O1C11)(20)
538w	532	532	β(O2=C11O1)(17)+β(O1C11C9)(16)+β(C7C5C3)(11)
	562	562	β(C18=C17C16)(21)+β(C19C18=C17)(19)
577vw	576	576	β(C15=C14C13)(13)+β(C16C15=C14)(13)
611vw	615	616	β(O2=C11O1)(18)+β(C12=C10C8)(11)+β(C13C12=C10)(12)
618vw	622	623	β(O2C11=O1)(27)
	658	659	τ(HO1C11C9)(11)+o(O2C9O1C11)(30)
	705	707	τ(HC10=C12C13)(29)+τ(HC12=C10C8)(31)
723vw	731	733	τ(HC3C5C7)(11)+τ(HC14=C15C16)(13)+τ(HC15=C14C13)(12)
733vw	733	735	τ(HC14=C15C16)(17)+τ(HC15=C14C13)(16)
	747	750	τ(HC4C6C8)(13)
767vw	758	761	τ(HC14=C15C16)(10)+τ(HC17=C18C19)(22)+τ(HC18=C17C16)(23)
	794	797	τ(HC20C19C18)(12)
	795	798	ν(C11C9)(10)+τ(HC20C19C18)(12)
845vw	845	849	ν(C11C9)(22)
851vw	855	860	ν(C4C6)(15)+ν(C7C5)(10)+τ(HC8C10=C12)(12)
866m	865	870	ν(C11C9)(31)+ν(C20C19)(14)+τ(HC20C19C18)(10)
879w	882	887	ν(C7C5)(11)+τ(HC9C11O1)(17)+ o(O2C9O1C11)(14)
903w	903	909	ν(C16C15)(14)+τ(HC16C17=C18)(14)
910w	913	919	ν(C16C15)(11)
942w	938	944	ν(C14C13)(14)+ν(C17C16)(10)
953w	953	960	ν(C16C15)(18)+τ(HC13C12=C10)(13)
975m	975	982	skeletal twisting
996	998	1006	ν(C14C13)(12)+ν(C20C19)(17)
1000vw	1001	1009	τ(HC10=C12C13)(15)+τ(HC12=C10C8)(22)
1006w	1008	1016	τ(HC15=C14C13)(11)
	1010	1018	τ(HC14=C15C16)(14)+τ(HC17=C18C19)(24)+τ(HC18=C17C16)(19)+τ(C19C18=C17C16)(12)
1014	1013	1021	τ(HC14=C15C16)(10)+τ(HC15=C14C13)(10)
	1020	1028	ν(C19C18)(10)+ν(C17C16)(13)+ν(C20C19)(28)
1024m	1025	1033	ν(C13C12)(13)
1041vw	1044	1053	ν(C3C4)(21)+ν(C5C3)(30)
1058vw	1057	1068	ν(C3C4)(14)+ν(C4C6)(14)+ν(C9C7)(12)+ν(C6C8)(16)
1069m	1062	1071	ν(C4C6)(13)+ν(C5C3)(13)+ν(C7C5)(18)
1076m	1072	1082	ν(C16C15)(10)+ν(C7C5)(11)
1082m	1081	1091	τ(HC19C18=C17)(16)+τ(HC20C19C18)(24)
1088m	1090	1100	ν(C4C6)(11)
1107w	1102	1112	ν(O1C11)(27)+β(HO1C11)(11)+β(HC7C9)(12)
1130w	1128	1139	τ(HC20C19C18)(10)
1152vw	1149	1161	skeletal twisting
1159w	1166	1178	ν(O1C11)(13)+β(HC7C9)(14)
1189vw	1191	1204	β(HC8C10)(13)+β(HC9C11)(13)
1202vw	1204	1218	β(HC13C14)(18)+β(HC16C17)(13)
1219vw	1224	1238	β(HC13C14)(18)+β(HC16C17)(21)+τ(HC16C17=C18)(11)
	1228	1242	β(HC8C10)(18)+β(HC9C11)(21)
1241m	1243	1258	τ(HC3C5C7)(12)+τ(HC5C7C9)(11)
1266vs	1265	1281	β(HC18C19)(13)+β(HC19C20)(20)+τ(HC19C18=C17)(12)
	1270	1286	skeletal twisting
	1271	1287	β(HC8C10)(12)+τ(HC3C5C7)(10)
	1279	1295	β(HC15C16)(13)+β(HC17=C18)(11)+β(HC19C20)(16)+τ(HC16C17=C18)(12)
	1282	1298	β(HO1C11)(20)+β(HC10=C12)(10)
1284s	1287	1303	β(HC18C19)(14)+β(HC16C17)(11)
	1289	1305	β(HC18C19)(14)+β(HC16C17)(11)
1298s	1297	1314	τ(HC16C17=C18)(12)
1303s	1303	1320	Skeletal vibration -(CH2)7- in phase twisting
	1315	1332	β(HC3C5)(14)+β(HC4C6)(27)+τ(HC6C8C10)(12)
	1316	1333	β(HC3C5)(26)+β(HC5C7)(18)+τ(HC4C6C8)(14)
1321w	1322	1340	β(HC4C6)(10)+β(HC5C7)(19)+β(HC7C9)(13)+τ(HC5C7C9)(12)
	1324	1342	τ(H₂C19C18=C17)(45)
1337w	1339	1357	β(HC6C8)(21)+τ(H₂C8C10C12)(25)
	1359	1378	τ(H₂C3C5C7)(21)+τ(H₂C6C8C10)(28)+τ(H₂C7C9C11)(21)
	1381	1401	τ(H₂C4C6C8)(34)
	1386	1406	τ(H₂C5C7C9)(35)+τ(H₂C7C9C11)(22)
1378vw	1388	1408	ν(C11C9)(11)+β(HC7C9)(11)+β(HC9C11)(12)+τ(HC9C11O1)(19)
	1389	1409	β(C20H₃)(85)
	1407	1428	β(HC14=C15)(35)+β(HC15C16)(32)
	1414	1435	β(HC17=C18)(33)+β(HC18C19)(29)
1416w	1417	1438	β(HC10C12)(35)+β(HC12C13)(34)
1442s	1438	1460	β(C9H₂)(81)
1450s	1449	1471	β(C8H₂)(11)+β(C13H₂)(55)+β(C16H₂)(21)
1457s	1458	1481	β(C8H₂)(18)+β(C18H₂)(41)+β(C19H₂)(20)
	1459	1482	β(C5H₂)(17)+β(C7H₂)(65)
	1463	1486	β(C3H₂)(17)+β(C6H₂)(39)
	1465	1488	β(C8H₂)(41)+β(C13H₂)(12)+β(C19H₂)(10)
	1466	1489	β(C8H₂)(41)+β(C13H₂)(12)+β(C19H₂)(10)
	1469	1492	β(C16H₂)(21)+β(C19H₂)(27)+β(C20H₂)(15)
1473w	1474	1498	β(C20H₃)(75)+τ(HC20C19C18)(15)
1484w	1483	1507	β(C19H₂)(22)+β(C20H₃)(48)
1494vw	1487	1511	β(C3H₂)(32)+β(C4H₂)(31)+β(C5H₂)(19)
1660vs	1670	1702	ν(C15=C14)(36)+ν(C18=C17)(36)
	1682	1715	ν(C12=C10)(52)+ν(C18=C17)(15)
	1686	1719	ν(C12=C10)(20)+ν(C15=C14)(32)+ν(C18=C17)(22)
	1772	1810	ν(O2=C11)(85)
2855vs	2856	2974	ν(C13H)(98)
	2873	2993	ν(C3H₂)(77)
	2874	2994	ν(C4H)(21)+ν(C6H₂)(31)+ν(C8H)(34)
2877vs	2878	2998	ν(C4H)(19)+ν(C5H)(49)+ν(C8H)(18)
2883vs	2882	3003	ν(C19H)(93)
2887vs	2889	3010	ν(C4H)(27)+ν(C6H₂)(37)
	2896	3018	ν(C3H₂)(56)+ν(C4H)(21)+ν(C5H)(11)
2898vs	2899	3022	ν(C7H)(45)+ν(C9H)(27)
2900vs	2900	3023	ns(C20H₃)(100)
	2906	3029	ν(C4H)(14)+ν(C6H₂)(57)
2908vs	2908	3031	ν(C16H₂)(95)
	2909	3032	ν(C7H₂)(33)+ν(C9H₂)(59)
	2920	3045	ν(C4H)(12)+ν(C5H)(45)+ν(C6H)(10)+ν(C7H)(16)
2925vs	2928	3053	ν(C4H)(19)+ν(C7H)(11)+ν(C8H)(30)
	2933	3059	ν(C16H₂)(40)+ν(C19H)(41)
2935vs	2934	3060	ν(C8H)(48)
	2939	3065	ν(C5H)(13)+ν(C9H₂)(55)
	2941	3068	ν(C16H₂)(44)+ν(C19H)(28)
	2949	3077	ν(C7H₂)(52)+ν(C9H)(32)
2959s	2959	3087	ν(C19H)(13)+ν(C20H)(93)
2965s	2963	3092	na(C20H₃)(90)
2968s	2968	3097	ν(C10H)(18)+ν(C12H)(20)+ν(C13H)(50)
	2972	3102	ν(C10H)(46)+ν(C12H)(13)+ν(C13H)(24)+ν(C14H)(13)
	2978	3106	ν(C17H)(24)+ν(C18H)(69)
	2981	3112	ν(C13H)(13)+ν(C14H)(47)+ν(C15H)(30)
	2995	3127	ν(C10H)(24)+ν(C12H)(62)
3014vs	3000	3133	ν(C17H)(74)+ν(C18H)(24)
	3003	3136	ν(C14H)(35)+ν(C15H)(57)
	3559	3756	ν(O1H)(100)

Atom. No	Atom	Charge value	Atom. No	Atom	Charge value
1	O	-0.092629	26	H	0.163846
2	O	-0.247065	27	H	0.147823
3	C	-1.024457	28	H	0.148889
4	C	0.531538	29	H	0.180420
5	C	0.408055	30	H	0.148503
6	C	-0.745203	31	H	0.150366
7	C	-0.489390	32	H	0.124910
8	C	-0.285638	33	H	0.173569
9	C	-0.320733	34	H	0.183291
10	C	-0.012076	35	H	0.115571
11	C	-0.214537	36	H	0.127846
12	C	-0.324474	37	H	0.122075
13	C	-0.133935	38	H	0.160727
14	C	-0.277082	39	H	0.124666
15	C	-0.440511	40	H	0.118567
16	C	0.324494	41	H	0.139245
17	C	-0.135037	42	H	0.158644
18	C	-0.236665	43	H	0.262171
19	C	-0.213247	44	H	0.116242
20	C	-0.483264	45	H	0.124706
21	H	0.146325	46	H	0.138516
22	H	0.150320	47	H	0.138268
23	H	0.166686	48	H	0.149711
24	H	0.139461	49	H	0.135472
25	H	0.147853	50	H	0.107167

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