Useful Analytical Data Atomic mass and n atural abundances of Degrees of unsaturation formula: common isotopes in organic molecules 12 C 98.89% 13 C 1.11% 1 H 99.99% 2 H 0.01% 14 N 99.64% 15 N 0.36% 16 O 99.76% 18 O 0.20% 35 Cl 75.77% 37 Cl 24.23% 79 Br 50.69% 81 Br 49.31% 19 F 100% 32 S 95.0% 34 S 4.22% 127 I 100% Significant IR Absorptions O – H 3600 – 3200 cm – 1 strong, broad N – H 3500 – 3200 cm – 1 medium C – H ~3000 cm – 1 C sp3 – H 3000 – 2850 cm – 1 medium/ strong C sp2 – H 3150 – 3000 cm – 1 medium C sp – H 3300 cm – 1 medium C ≡ C 2250 cm – 1 (medium) med i um C ≡ N 2250 cm – 1 (medium) medium C=O 1800 – 1650 cm – 1 (often ~1700 cm – 1 ) strong C=C 1650 cm – 1 medium 1600, 1500 cm – 1 medium Key NMR Regions C C H C C H C C C H O Z C H (Z = O, N, halogen) C H C H C H O C O H O 0 1.5 2.5 4.5 6.5 8.0 9.0 10.5 12.0 C O H C N H and 1 H NMR 0 20 40 60 80 100 120 140 160 180 200 220 C–C (alkyl) C C C C (alkene) C–X (alkyl) aromatic (benzene) O 13 C NMR R R O R X