S. No. Observed    frequency Calculated frequency HF B3LYP B3PW91 6-311+G (d, p) 6-31+G (d, p) 6-311+G (d, p) 6-31+G (d, p) 6-311+G (d, p) 1 3090w 3347 3187 3187 3211 3198 2 3080m 3333 3174 3174 3199 3185 3 3070m 3323 3166 3165 3190 3176 4 3060m 3310 3152 3152 3176 3163 5 3040s 3307 3151 3151 3175 3161 6 3030s 3220 3084 3084 3115 3105 7 3010w 3217 3081 3081 3110 3100 8 3005w 3199 3059 3058 3089 3077 9 2960s 3178 3037 3037 3069 3055 10 2940s 3167 3023 3023 3050 3035 11 2930s 3160 3017 3017 3044 3028 12 2910m 3151 3013 3012 3041 3025 13 1610w 1789 1643 1643 1684 1658 14 1605w 1762 1622 1622 1661 1636 15 1590w 1649 1525 1525 1548 1527 16 1500s 1629 1510 1510 1518 1502 17 1495s 1614 1497 1497 1505 1491 18 1455m 1614 1495 1495 1503 1488 19 1450s 1607 1487 1487 1501 1482 20 1440w 1598 1482 1482 1496 1479 21 1380w 1537 1411 1411 1423 1403 22 1340w 1513 1382 1382 1402 1378 23 1290w 1471 1361 1361 1371 1363 24 1280w 1429 1342 1342 1343 1353 25 1250w 1423 1322 1322 1328 1319 26 1200s 1366 1316 1316 1328 1308 27 1190w 1321 1248 1248 1257 1244 28 1180w 1309 1226 1226 1244 1231 29 1160w 1287 1202 1202 1210 1199 30 1105w 1231 1181 1181 1184 1178 31 1100w 1199 1124 1124 1132 1122 32 1095w 1168 1108 1108 1126 1110 33 1050w 1139 1070 1070 1082 1070 34 1040w 1119 1050 1050 1066 1057 35 1030w 1110 1038 1038 1062 1052 36 1000s 1104 1017 1017 1030 1016 37 910w 1097 1001 996 1026 995 38 895w 1081 982 980 1007 980 39 890w 1026 929 927 949 926 40 865w 959 894 894 912 900 41 840w 947 879 879 886 874 42 820w 938 854 853 872 853 43 740vs 881 824 824 838 826 44 705vs 826 761 760 776 761 45 700vs 794 746 746 751 741 46 610m 772 712 712 724 712 47 590s 678 636 636 642 632 48 570vs 640 598 599 606 595 49 530vw 547 507 507 515 505 50 490s 452 413 414 420 411 51 480s 369 346 346 350 343 52 470vw 330 309 309 314 309 53 400 m 301 278 278 282 275 54 370m 258 229 229 234 229 55 280s 112 102 102 103 101 56 270s 91 83 83 85 83 57 260s 40 45 45 40 44

Table 3: Calculated unscaled frequencies of propyl benzene using HF/DFT (B3LYP&B3PW91) with 6-31+(d,p) and 6-311+G(d,p) basis sets.