1. Ab Initio and DFT Calculations for the Vibrational Frequencies and Barrier to Planarity of Cyclopentene and its Deuterated Isotopomers Abdulaziz Al-Saadi and Jaan Laane Department of Chemistry Texas A&M University College Station, Texas

2. 2 Cyclopentene-d 0, -d 1, -d 4, and -d 8 We had previously determined the IR and Raman spectra, calculated the 1D and 2D PES, and ran a MM investigation of the four molecules. Cyclopentene exists in the puckered form with a puckering angle of 26º based on spectroscopic determination. Planar Puckered C 2v CsCs CsCs C1C1 Symmetry Species11A 1 + 6A 2 + 9B 1 + 7B 2 20A ’ + 13A ” φ = 26 o C2C2 z x (1) Villarreal, J. R.; Laane, J.; Bush, S. F.; Harris, W. C., Spectrochem. Acta, 1979, 35A, 331. (2) Laane, J., Lord, R. C., J. Chem. Phys., 1967, 47, 4941. (3) Rosas, R. L., Cooper, C., and Laane, J., J. Chem. Phys., 1990, 94,1830. 1-3

3. 3 Cyclopentene-d 0, -d 1, -d 4, and -d 8 In this work we: Optimized the structure cyclopentene-d 0 in the planar and puckered conformations using the MP2 and DFT theories with the 6-311++G** and cc-pVTZ basis sets. Predicted the zero-point energy, puckering barrier and puckering angle of cyclopentene-d 0. Calculated the vibrational frequencies of the two structures for cyclopentene-d 0, -d 1, -d 4, and -d 8 molecules from density functional theory and then compared the assignments with the experimental ones. Made several vibrational reassignments for the d 0, d 1, d 4 and d 8 isotopomers. Obtained the liquid IR and Raman spectra for cyclopentene-d 0 to help confirm our reassignments.

4. 4 Calculated Structure of Cyclopentene-d 0 C 2v CsCs

5. 5 Experimental and Calculated Puckering Barrier and Puckering Angle Expt. Calculated MP2/DZ 1 MP2/ 6-311++G** MP2/ cc-pVTZ DFT-B3LYP/ 6-311++G** DFT-B3LYP/ cc-pVTZ τ 2.3  3.0  3.1  2.3  2.1  φ 28.8  GED 2 23.4  27.1  26.1  20.0  19.3  22.2  MW 3 26  Far-IR 4 Puckering Barrier (cm -1 ) 233 4 177.1297.97246.68 59.78 41.68 H τ φ (1) Allen, W. D.; Csaszar, A. G.; Horner, D. A., J. Am. Chem. Soc., 1992, 114, 6834. (2) Davis, M. I.; Mueche, T. W.; J. Phys. Chem., 1970, 74, 1104. (3) Rathjens, G. W., J. Chem. Phys., 1962, 36, 2401. (4) Laane, J., Lord, R. C., J. Chem. Phys., 1967, 47, 4941.

6. 6 Calculated Ring-Puckering & Ring-Twisting Frequencies in Cyclopentene-d 0, -d 1, -d 4, and -d 8 Expt. puck 1 twist 2 Calculated (Scaled) B3LYP/6-311++G**B3LYP/cc-pVTZ IRIR Rampucktwistpucktwist d0d0 127 390135385130387 d1d1 126369 137370129372 d4d4 120337 338128337120338 d8d8 108 317109318103320 Ring Twisting ( 17 )Ring Puckering ( 33 ) (1) Laane, J., Lord, R. C., J. Chem. Phys., 1967, 47, 4941. (2) Villarreal, J. R.; Laane, J.; Bush, S. F.; Harris, W. C., Spectrochem. Acta, 1979, 35A, 331.

7. 7 Assignments Observed * Calculated (Scaled) at DFT-B3LYP Vapor IR 1 Vapor Raman 1 Liquid IR 2 CsCs C 2v 6-311++G**cc-pVTZ6-311++G**cc-pVTZ A1A1 1 CH sym. str. 3078 s3070 (140)3057(23,187)3068(23,186)3064(23,187)3066(24,187) 2 β-CH 2 sym. str. 2903 s2900 (7)2897 m2935(55,183)2937(56,173)2939(46,168)2942(44,154) 3 α-CH 2 sym. str. (i.p.) 2860 s2857 (153)2848 vs2879(31,240)2881(31,218)2913(1,282)2896(2,267) 4 C=C str. 1623 m1617 (91)1610 m1640(3,250)1649(2,143)1650(4,206)1657(3,125) 5 β-CH 2 def. 1471 vw1473 (16)1479(3,43)1481(2,57)1485(4,41)1486(3,56) 6 α-CH 2 def. (i.p.) 1445 m1448 (23)1463 m1454(2,136)1459(1,143)1459(0,129)1459(0,138) 7 α-CH 2 wag (i.p.) 1290 m1302 (10)1295 m1300(1,21)1303(1,21)1303(1,18)1306(1,19) 8 CH in-plane bend (i.p.) 1101 w1109 (66)1108 vw1107(0,136)1111(0,129)1108(0,118)1112(0,119) 9 Ring str. 962 w 962 (55) 963 m954(1,57)955(1,50)957(1,35)958(1,31) 10 Ring breathing 900 m 896 (100) 903 s885(1,100)885(0,100)875(0,100)875(0,100) 11 Ring def. 608 w 600 (1) 603 m604(14,7)608(12,7)689(0,5)691(0,11) A2A2 12 α-CH 2 antisym. str. (o.p.) 2938 (54)2924(37,121)2924(37,120)2913(0,188)2913(0,184) 13 α-CH 2 twist (o.p.) 1209 (2)1279 w1282(2,7)1287(2,7)1249(0,23)1253(0,25) 14 β-CH 2 twist 1134 (1)1131(2,0)1132(1,0)1139(0,2)1140(0,3) 15 CH out-of-plane bend (o.p.) 1047 (1)955(0,7)961(0,7)958(0,10)965(0,5) 16 α-CH 2 rock (o.p.) 879 (1)872(4,7)875(4,7)889(0,4)893(0,3) 17 Ring twist 390 (2)385(0,14)387(0,21)370(0,8)374(0,11) B1B1 18 CH antisym. str. 3068 s3062 (18)3055 s3043(8,87)3044(8,87)3040(8,88)3043(8,87) 19 α-CH 2 sym. str. (o.p.) 2873 s2882 (57)2866 s2880(55,82)2883(54,75)2895(97,40)2896(95,33) 20 α-CH 2 def. (o.p.) 1438 vw1444 m1460(3,71)1463(2,71)1464(3,53)1466(2,56) 21 CH in-plane bend (o.p.) 1353 m1354 (2)1350 vw1351(2,0)1358(2,0)1352(2,1)1360(1,3) 22 α-CH 2 wag (o.p.) 1268 m1297 (5)1291(0,7)1296(0,7)1287(2,0)1295(1,0) 23 β-CH 2 wag 1128 w1167 vw1201(0,36)1205(0,29)1246(0,25)1247(1,19) 24 Ring str. 1037 w1030 (1)1025 w1014(2,36)1015(2,29)1018(2,24)1071(2,18) 25 Ring str. 933 w 933 (2)899(8,0)900(7,0)891(12,7)891(11,5) 26 Ring def. 695 s 690 (1) 770 vw768(0,7)771(0,7)773(1,6)776(1,4) B2B2 27 α-CH 2 antisym. str. (i.p.) 2963 s2973 (39)2949 s2969(44,87)2970(43,84)2972(43,74)2973(43,74) 28 β-CH 2 antisym. str. 2933 s2929 (30)2925 s2916(5,66)2918(4,61)2910(33,3)2910(35,2) 29 α-CH 2 twist (i.p.) 1207 m1205 m1207(2,50)1209(2,43)1201(2,40)1204(2,38) 30 α-CH 2 rock (i.p.) 1047 s1047 (1)1043 s1047(8,7)1052(7,7)1042(9,2)1048(8,3) 31 CH out-of-plane bend (i.p.) 695 s 696 s699(39,14)702(31,21)660(46,8)663(37,16) 32 β-CH 2 rock 593 m 803 vw802(1,7)803(1,7)766(8,9)770(7,11) 33 Ring puckering 127.1135(0,14)130(0,7) Experimental and Calculated Frequencies for Cyclopentene (1) Villarreal, J. R.; Laane, J.; Bush, S. F.; Harris, W. C., Spectrochem. Acta, 1979, 35A, 331. (2) This work. * Values shown in italic are from condensed-phase experiments.

8. 8 Vibrational Reassignments for Cyclopentene Assignments Observed * Calculated (Scaled) at DFT-B3LYP Vapor IR 1 Vapor Raman 1 Liquid IR 2 CsCs C 2v 6-311++G**cc-pVTZ6-311++G**cc-pVTZ A1A1 1 CH sym. str. 3078 s3070 (140)3057(23,187)3068(23,186)3064(23,187)3066(24,187) 2 β-CH 2 sym. str. 2903 s2900 (7)2897 m2935(55,183)2937(56,173)2939(46,168)2942(44,154) 3 α-CH 2 sym. str. (i.p.) 2860 s2857 (153)2848 vs2879(31,240)2881(31,218)2913(1,282)2896(2,267) 4 C=C str. 1623 m1617 (91)1610 m1640(3,250)1649(2,143)1650(4,206)1657(3,125) 5 β-CH 2 def. 1471 vw1473 (16)1479(3,43)1481(2,57)1485(4,41)1486(3,56) 6 α-CH 2 def. (i.p.) 1445 m1448 (23)1463 m1454(2,136)1459(1,143)1459(0,129)1459(0,138) 7 α-CH 2 wag (i.p.) 1290 m1302 (10)1295 m1300(1,21)1303(1,21)1303(1,18)1306(1,19) 8 CH in-plane bend (i.p.) 1101 w1109 (66)1108 vw1107(0,136)1111(0,129)1108(0,118)1112(0,119) 9 Ring str. 962 w 962 (55) 963 m954(1,57)955(1,50)957(1,35)958(1,31) 10 Ring breathing 900 m 896 (100) 903 s885(1,100)885(0,100)875(0,100)875(0,100) 11 Ring def. 593 m 600 (1) 603 m604(14,7)608(12,7)689(0,5)691(0,11) A2A2 12 α-CH 2 antisym. str. (o.p.) 2938 (54)2924(37,121)2924(37,120)2913(0,188)2913(0,184) 13 α-CH 2 twist (o.p.) 1268 m 1279 w1282(2,7)1287(2,7)1249(0,23)1253(0,25) 14 β-CH 2 twist 1128 w 1134 (1)1131(2,0)1132(1,0)1139(0,2)1140(0,3) 15 CH out-of-plane bend (o.p.) 955(0,7)961(0,7)958(0,10)965(0,5) 16 α-CH 2 rock (o.p.) 879 (1)872(4,7)875(4,7)889(0,4)893(0,3) 17 Ring twist 390 (2)385(0,14)387(0,21)370(0,8)374(0,11) B1B1 18 CH antisym. str. 3068 s3062 (18)3055 s3043(8,87)3044(8,87)3040(8,88)3043(8,87) 19 α-CH 2 sym. str. (o.p.) 2873 s2882 (57)2866 s2880(55,82)2883(54,75)2895(97,40)2896(95,33) 20 α-CH 2 def. (o.p.) 1438 vw1444 m1460(3,71)1463(2,71)1464(3,53)1466(2,56) 21 CH in-plane bend (o.p.) 1353 m1354 (2)1350 vw1351(2,0)1358(2,0)1352(2,1)1360(1,3) 22 α-CH 2 wag (o.p.) 1297 (5)1291(0,7)1296(0,7)1287(2,0)1295(1,0) 23 β-CH 2 wag 1167 vw1201(0,36)1205(0,29)1246(0,25)1247(1,19) 24 Ring str. 1037 w1030 (1)1025 w1014(2,36)1015(2,29)1018(2,24)1071(2,18) 25 Ring str. 933 w 933 (2)899(8,0)900(7,0)891(12,7)891(11,5) 26 Ring def. 770 vw768(0,7)771(0,7)773(1,6)776(1,4) B2B2 27 α-CH 2 antisym. str. (i.p.) 2933 s 2929 (30)2925 s2916 (5,66) 2918 (4,61) 2910 (33,3) 2910 (35,2) 28 β-CH 2 antisym. str. 2963 s2973 (39)2949 s2969 (44,87) 2970 (43,84) 2972 (43,74) 2973 (43,74) 29 α-CH 2 twist (i.p.) 1207 m 1209 (2) 1205 m1207(2,50)1209(2,43)1201(2,40)1204(2,38) 30 α-CH 2 rock (i.p.) 1047 s1047 (1)1043 s1047(8,7)1052(7,7)1042(9,2)1048(8,3) 31 CH out-of-plane bend (i.p.) 695 s 690 (1) 696 s699(39,14)702(31,21)660(46,8)663(37,16) 32 β-CH 2 rock 803 vw802(1,7)803(1,7)766(8,9)770(7,11) 33 Ring puckering 127.1135(0,14)130(0,7) (1) Villarreal, J. R.; Laane, J.; Bush, S. F.; Harris, W. C., Spectrochem. Acta, 1979, 35A, 331. (2) This work. * Values shown in italic are from condensed-phase experiments.

9. 9 Vibrational Reassignments for Cyclopentene-d 8 Assignments Observed * Calculated (Scaled) at DFT-B3LYP Vapor IR 1 Vapor Raman 1 CsCs C 2v 6-311++G**cc-pVTZ6-311++G**cc-pVTZ A1A1 1 CD sym. str. 2310 s2305 (68)2314(9,74)2315(9,78)2313(9,74)2314(10,78) 2 β-CD 2 sym. str. 2153 w2145 (100)2157(18,75)2160(18,67)2166(23,84)2168(22,77) 3 α-CD 2 sym. str. (i.p.) 2100 (136)2126(11,141)2128(10,132)2132(0,143)2135(1,134) 4 C=C str. 1580 m1577 (50)1591(6,205)1600(4,143)1602(6,76)1609(5,123) 5 β-CD 2 def. 1110 w1113 (7)1109(1,14)1110(1,14)1110(2,13)1110(1,11) 6 α-CD 2 def. (i.p.) 1070 m1072 (2)1068(1,18)1071(1,19)1069(0,16)1072(0,18) 7 α-CD 2 wag (i.p.) 750 w 750 (7)743(1,14)744(1,13)749(1,16)750(0,14) 8 CD in-plane bend (i.p.) 853 w 850 (7)783(0,32)785(0,38)779(0,33)781(0,33) 9 Ring str. 1150 vw1158 (2)1148(0,6)1149(1,4)1149(0,4)1148(0,6) 10 Ring breathing 878 m 878 (100)869(3,100)871(2,100)863(1,100)865(0,100) 11 Ring def. 682(0,4)681(0,3)643(0,5)645(0,6) A2A2 12 α-CD 2 antisym. str. (o.p.) 2202 (15)2191(7,79)2190(7,79)2185(0,98)2186(0.96) 13 α-CD 2 twist (o.p.) 868 w 860 (5)887(2,18)890(1,19)888(0,16)891(0,16) 14 β-CD 2 twist 921 w 930 (1)926(0,5)929(0,4)926(0,4)930(0,2) 15 CD out-of-plane bend (o.p.) 724 m 720 (6)725(2,5)728(1,3)730(0,4)733(0,4) 16 α-CD 2 rock (o.p.) 667658(0,0)661(0,0)670(0,0)673(0,0) 17 Ring twist 317 (2)318(0,6)320(2,9)305(0,4)308(0,7) B1B1 18 CD antisym. str. 2276 m2268 (15)2268(3,44)2270(3,44)2267(3,44)2268(3,44) 19 α-CD 2 sym. str. (o.p.) 2138 m2132 (20)2126(37,29)2128(38,24)2131(47,24)2133(46,19) 20 α-CD 2 def. (o.p.) 1062 m1060(2,14)1062(2,14)1058(2,11)1059(1,9) 21 CD in-plane bend (o.p.) 709 w 715705(7,5)707(6,2)705(9,2)706(8,2) 22 α-CD 2 wag (o.p.) 1024 vw1020(1,0)1027(1,0)1023(1,0)1029(1,0) 23 β-CD 2 wag 790 (7)786(0,23)788(0,20)804(0,19)804(0,14) 24 Ring str. 1124(1,4)1122(1,3)1114(1,5)1113(1,6) 25 Ring str. 1191(0,9)1195(0,10)1195(1,9)1198(1,9) 26 Ring def. 754(1,1)757(1,0)758(1,1)760(1,3) B2B2 27 α-CD 2 antisym. str. (i.p.) 2200 s2202 (15)2193(22,34)2192(23,31)2185(24,3)2186(24,2) 28 β-CD 2 antisym. str. 2230 s2235 (30)2229(22,41)2230(22,40)2232(20,36)2233(20,37) 29 α-CD 2 twist (i.p.) 849 s848(6,27)852(5,29)854(9,9)857(8,9) 30 α-CD 2 rock (i.p.) 954 w 950 (1)951(0,10)954(0,8)939(0,7)943(0,5) 31 CD out-of-plane bend (i.p.) 465 s 460 (1)460(16,5)464(13,3)481(24,3)483(19,6) 32 β-CD 2 rock 543 s 550 (1)546(13,4)549(10,8)571(5,3)574(4,4) 33 Ring puckering 108.2109(0,3)103(0,1) (1) Villarreal, J. R.; Laane, J.; Bush, S. F.; Harris, W. C., Spectrochem. Acta, 1979, 35A, 331. * Values shown in italic are from condensed-phase experiments.

10. 10 Vibrational Reassignments for 1-Cyclopentene-d 1 Assignments Observed (*) Calculated (Scaled) at DFT-B3LYP Vapor IR 1 Vapor Raman 1 C1C1 CsCs 6-311++G**cc-pVTZ6-311++G**cc-pVTZ A’ 1 CH str. 3065 m3066 (188)3054(15,138)3056(16,138)3051(15,139)3054(16,139) 2 β-CH 2 sym. str. 2903 s2904 (122)2935(53,188)2937(54,178)2939(45,172)2943(43,157) 3 α-CH 2 sym. str. 2865 s2879 (105)2880(54,80)2882(53,74)2895(25,225)2897(12,246) 4 α-CH 2 sym. str 2859 s2859 (224)2879(32,242)2881(31,220)2895(73,99)2896(85,57) 5 =C-D str. 2294 m2290 (37)2291(6,54)2293(7,55)2288(6,54)2291(7,56) 6 C=C str. 1600 m1597 (79)1619(4,270)1628(3,177)1628(5,229)1637(4,153) 7 β-CH 2 def. 1470 m1472 (22)1479(3,42)1481(2,62)1484(4,41)1486(3,66) 8 α-CH 2 def. 1446 m1448 (32)1461(3,76)1464(2,77)1463(3,53)1466(2,60) 9 α-CH 2 def. 1435 w1455(2,136)1458(1,154)1455(0,124)1459(0,153) 10 CH in-plane bend 1261 m1257 (3)1254(1,21)1263(1,15)1260(1,16)1266(1,14) 11 α-CH 2 wag 1300 w1298 (10)1299(1,13)1303(1,17)1302(1,12)1305(1,13) 12 α-CH 2 wag 1322 s1327 (5)1324(2,4)1329(2,6)1325(2,4)1330(2,9) 13 β-CH 2 wag 1116 w1121 (1)1286(2,11)1288(2,14)1240(0,31)1242(0,21) 14 Ring str. 1033 m1029 (8)1019(3,39)1020(3,38)1023(3,29)1023(3,31) 15 CD in-plane bend 988 w 978 (65)969(1,86)971(2,85)965(2,76)967(2,64) 16 Ring str. 966 w 952 (33)945(2,49)946(2,38)950(2,35)950(1,33) 17 Ring breathing 893 w 899 (100)886(2,100)886(2,100)876(1,100)877(1,100) 18 Ring str. 750 w 750 (1)745(3,6)747(3,15)748(3,12)751(3,13) 19 Ring def. 698 w 708 (8)772(1,7)774(1,8)797(3,11)800(3,10) 20 Ring def. 634 s 630 (1)638(6,5)642(4,6)680(0,5)683(0,6) A” 21 α-CH 2 antisym. str. 2939 s2939 (126)2925(38,118)2925(38,117)2913(0,188)2913(0,184) 22 α-CH 2 antisym. str. 2939 s2924 (126)2917(6,66)2918(4,61)2911(3,33)2910(35,2) 23 β-CH 2 antisym. str. 2962 s2969 (60)2969(44,87)2969(43,84)2972(43,74)2973(43,74) 24 α-CH 2 twist 1211 s1202 (2)1206(2,46)1208(2,43)1200(1,40)1203(1,41) 25 α-CH 2 twist 1137 w11381131(2,1)1133(1,2)1139(0,2)1140(0,3) 26 β-CH 2 twist 1207 w1196(0,45)1199(0,38)1249(0,22)1253(0,27) 27 α-CH 2 rock 1044 s10451043(6,5)1048(6,5)1038(7,2)1044(6,5) 28 CH out-of-plane bend 897(2,15)902(2,17)910(1,18)915(1,13) 29 α-CH 2 rock 855 s 855 (1)860(4,3)864(3,18)861(5,4)866(4,10) 30 β-CH 2 rock 812(3,4)813(3,6)744(0,1)747(0,4) 31 CD out-of-plane bend 565 s 565 (1)563(30,7)567(25,15)578(37,7)579(30,12) 32 Ring twist 369 w 369 (3)370(0,5)372(0,10)355(0,5)359(0,12) 33 Ring puckering 126137(0,3)129(0,4) (1) Villarreal, J. R.; Laane, J.; Bush, S. F.; Harris, W. C., Spectrochem. Acta, 1979, 35A, 331. * Values shown in italic are from condensed-phase experiments.

11. 11 Assignments Observed * Calculated (Scaled) at DFT-B3LYP Vapor IR 1 Vapor Raman 1 C1C1 CsCs 6-311++G**cc-pVTZ6-311++G**cc-pVTZ A’ 1 CD str. 2310 m2313 (13)2314(10,67)2315(11,71)2312(10,68)2314(11,72) 2 β-CH 2 sym. str. 2941 s2941 (20)2933(52,165)2934(52,156)2938(43,146)2941(41,134) 3 α-CD 2 sym. str. 2110 s2100 (51)2127(24,95)2128(24,87)2134(25,97)2135(24,89) 4 α-CH 2 sym. str 2854 s2861 (46)2879(41,167)2882(41,152)2895(49,167)2897(48,156) 5 =C-D str. 2277 m2265 (5)2268(3,45)2270(3,44)2266(3,45)2268(3,44) 6 C=C str. 1560 m1580 (51)1595(4,195)1604(4,141)1605(6,191)1613(5,132) 7 β-CH 2 def. 1460 m1467 (4)1474(3,23)1477(1,27)1480(3,22)1483(2,30) 8 α-CH 2 def. 1449 m1452 (7)1457(2,72)1459(1,82)1458(1,74)1461(1,77) 9 α-CD 2 def. 1081 vw1085 (4)1081(0,18)1084(0,20)1082(0,17)1085(0,22) 10 CD in-plane bend 800 w 802 (3)796(0,27)798(0,28)792(0,28)793(0,32) 11 α-CH 2 wag 1286 w1290 (1)1284(1,9)1286(1,10)1270(1,13)1272(1,18) 12 α-CD 2 wag 821 m 825 (7)813(1,18)815(1,22)822(1,30)823(1,27) 13 β-CH 2 wag 1027 w1309(2,4)1314(1,8)1310(2,2)1315(1,2) 14 Ring str. 1107 m1100 (1)1101(3,8)1104(2,6)1099(3,8)1102(2,8) 15 CD in-plane bend 715 vw 719714(2,3)715(2,4)716(7,4)719(7,4) 16 Ring str. 1143 w1151(0,10)1153(0,7)1164(1,9)1167(1,9) 17 Ring breathing 910 m 910 (100)901(1,100)903(1,100)894(1,100)897(1,100) 18 Ring str. 985 vw 985 (2)973(0,23)974(0,20)979(0,17)978(0,14) 19 Ring def. 725 w 726 (1)767(1,6)769(1,9)769(2,4)771(2,3) 20 Ring def. 604 m 604 (1)603(4,3)607(4,5)661(0,5)664(0,4) 599 s A” 21 α-CH 2 antisym. str. 2904 s2905 (20)2919(18,78)2920(17,74)2912(17,92)2913(18,90) 22 α-CD 2 antisym. str. 2200 s2194 (10)2192(16,55)2191(16,53)2187(15,53)2187(15,51) 23 β-CH 2 antisym. str. 2964 s2969 (30)2967(37,87)2969(36,84)2970(33,71)2971(33,72) 24 α-CH 2 twist 1163 vw1160 (1)1163(2,16)1166(1,15)1160(0,11)1162(0,14) 25 α-CD 2 twist 872 s 875 (4)872(4,20)875(3,24)874(4,13)878(3,11) 26 β-CH 2 twist 12261211 (1)1226(0,13)1229(0,15)1236(0,22)1240(0,19) 27 α-CH 2 rock 1041 s1045 (1)1038(2,8)1042(2,4)1031(1,4)1037(1,3) 28 CD out-of-plane bend 735 w 733 (1)733(3,8)736(3,4)723(1,4)729(1,3) 29 α-CD 2 rock 703(2,1)706(2,2)666(1,5)669(0,1) 30 β-CH 2 rock 858 m 860 (3)848(1,4)849(1,8)841(0,3)844(0,2) 31 CD out-of-plane bend 502 s 500 (1)502(28,2)506(23,8)511(31,4)514(26,12) 32 Ring twist 337 w 338 (2)337(0,4)338(0,6)323(0,3)327(0,7) 33 Ring puckering 120.0128(0,3)120(0,2) Vibrational Reassignments for 1,2,3,3-Cyclopentene-d 4 (1) Villarreal, J. R.; Laane, J.; Bush, S. F.; Harris, W. C., Spectrochem. Acta, 1979, 35A, 331. * Values shown in italic are from condensed-phase experiments.

12. 12 Numbers of Revised Assignments in Cyclopentene-d 0, -d 1, -d 4, and -d 8 # of Vibrations Reassigned Cyclopentene-d 0 5 Cyclopentene-d 1 7 Cyclopentene-d 4 16 Cyclopentene-d 8 14

13. 13 Experimental (Liquid-phase) and Calculated Infrared Spectra of Cyclopentene 5x 4x

14. 14 Experimental (Liquid-phase) and Calculated Raman Spectra of Cyclopentene 10x5x

15. 15 Conclusions Conformational structures and vibrational frequencies of cyclopentene and its deuterated isotopomers were studied with ab initio calculations, and the results were compared with previously reported experimental results. The barrier to planarity predicted by the MP2 theory (247 cm -1 ) agrees very well with our previously far-IR data (233 cm -1 ). The DFT barrier (42 cm -1 ), however, was predicted to be considerably low. DFT calculated frequencies using the 6-311++G** and cc-pVTZ basis sets agree very well with experimental frequencies (even though the calculated band intensities are not as good) and help in reassigning some vibrational modes in the four molecules. The MP2 method gives a more reliable prediction of the calculated energies and structures while the DFT method predicts the frequencies very well.

16. 16 Acknowledgments The National Science Foundation. The Robert A. Welch Foundation. The Texas Advance Research Program.

17. 17 Calculated Structure of Cyclopentene-d 0 C 2v CsCs

18. 18 Assignments Observed 1 Calculated (Scaled) at DFT-B3LYP Comments from Calculation Vapor IR * Vapor Raman * CsCs C 2v 6-311++G**cc-pVTZ6-311++G**cc-pVTZ A1A1 1 CD sym. str. 2310 s2305 (68)2314(9,74)2315(9,78)2313(9,74)2314(10,78) 2 β-CD 2 sym. str. 2153 w2145 (100)2157(18,75)2160(18,67)2166(23,84)2168(22,77) 3 α-CD 2 sym. str. (i.p.) 2100 (136)2126(11,141)2128(10,132)2132(0,143)2135(1,134) 4 C=C str. 1580 m1577 (50)1591(6,205)1600(4,143)1602(6,76)1609(5,123) 5 β-CD 2 def. 1110 w1113 (7)1109(1,14)1110(1,14)1110(2,13)1110(1,11) 6 α-CD 2 def. (i.p.) 1070 m1072 (2)1068(1,18)1071(1,19)1069(0,16)1072(0,18) 7 α-CD 2 wag (i.p.) 921 w 930 (1)926(0,5)929(0,4)926(0,4)930(0,2) 14 8 CD in-plane bend (i.p.) 853 w 850 (7)783(0,32)785(0,38)779(0,33)781(0,33) 9 Ring str. 750 w 750 (7)743(1,14)744(1,13)749(1,16)750(0,14) 7 10 Ring breathing 878 m 878 (100)869(3,100)871(2,100)863(1,100)865(0,100) 11 Ring def. 574 w ?682(0,4)681(0,3)643(0,5)645(0,6) A2A2 12 α-CD 2 antisym. str. (o.p.) 2202 (15)2191(7,79)2190(7,79)2185(0,98)2186(0.96) 13 α-CD 2 twist (o.p.) 790 (7)786(0,23)788(0,20)804(0,19)804(0,14) 23 14 β-CD 2 twist 1124(1,4)1122(1,3)1114(1,5)1113(1,6) 24 15 CD out-of-plane bend (o.p.) 754(1,1)757(1,0)758(1,1)760(1,3) 26 16 α-CD 2 rock (o.p.) 667658(0,0)661(0,0)670(0,0)673(0,0) 17 Ring twist 317 (2)318(0,6)320(2,9)305(0,4)308(0,7) B1B1 18 CD antisym. str. 2276 m2268 (15) 2268(3,44)2270(3,44)2267(3,44)2268(3,44) 19 α-CD 2 sym. str. (o.p.) 2138 m2132 (20) 2126(37,29)2128(38,24)2131(47,24)2133(46,19) 20 α-CD 2 def. (o.p.) 1062 m 1060(2,14)1062(2,14)1058(2,11)1059(1,9) 21 CD in-plane bend (o.p.) 1150 vw1158 (2) 1148(0,6)1149(1,4)1149(0,4)1148(0,6) 9 22 α-CD 2 wag (o.p.) 954 w 950 (1) 951(0,10)954(0,8)939(0,7)943(0,5) 30 23 β-CD 2 wag 868 w 860 (5) 887(2,18)890(1,19)888(0,16)891(0,16) 13 24 Ring str. 1024 vw 1020(1,0)1027(1,0)1023(1,0)1029(1,0) 25 Ring str. 724 m 720 (6) 725(2,5)728(1,3)730(0,4)733(0,4) 15 26 Ring def. 709 w 715 705(7,5)707(6,2)705(9,2)706(8,2) 21 B2B2 27 α-CD 2 antisym. str. (i.p.) 2230 s2235 (30) 2229(22,41)2230(22,40)2232(20,36)2233(20,37) 28 28 β-CD 2 antisym. str. 2200 s2202 (15) 2193(22,34)2192(23,31)2185(24,3)2186(24,2) 27 29 α-CD 2 twist (i.p.) 878 m 878 1191(0,9)1195(0,10)1195(1,9)1198(1,9) 25 30 α-CD 2 rock (i.p.) 849 s 848(6,27)852(5,29)854(9,9)857(8,9) 29 31 CD out-of-plane bend (i.p.) 543 s 550 (1) 546(13,4)549(10,8)571(5,3)574(4,4) 32 32 β-CD 2 rock 465 s 460 (1) 460(16,5)464(13,3)481(24,3)483(19,6) 31 33 Ring puckering 108.2 109(0,3)103(0,1)---- (1) Villarreal, J. R.; Laane, J.; Bush, S. F.; Harris, W. C., Spectrochem. Acta, 1979, 35A, 331. * Values shown in italic are from condensed-phase experiments. Experimental and Calculated Frequencies for Cyclopentene-d 8