Spectroscopy Data Tables 1 Infrared Tables (short ... - CPP

1 Spectroscopy Data Tables 1. Infrared Tables (short summary of common absorption frequencies). The values given in the Tables that follow are typical values. Specific bands may fall over a range of wavenumbers, cm-1. Specific substituents may cause variations in absorption frequencies. Absorption intensities may be stronger or weaker than expected, often depending on dipole moments. Additional bands may confuse the interpretation. In very symmetrical compounds there may be fewer than the expected number of absorption bands (it is even possible that all bands of a functional group may disappear, a symmetrically substituted alkyne!). Infrared spectra are generally informative about what functional groups are present, but not always. The 1H and 13C NMR's are often just as informative about functional groups, and sometimes even more so in this regard.

2 Information obtained from one spectroscopic technique should be verified or expanded by consulting the other spectroscopic techniques. IR Summary - All numerical values in the Tables below are given in wavenumbers, cm-1. Bonds to Carbon (stretching wave numbers). sp3 C-X single bonds sp2 C-X single bonds C N C O C O. C C C C C N. 1000-1350 1050-1150 1100-1350. not used not very useful alkoxy C-O not very useful 1250 acyl and phenyl C-O. sp2 C-X double bonds sp C-X triple bonds C O. C C C N. C C C N. 1640-1810. expanded table 1600-1680 1640-1690 on next page 2100-2250 2240-2260. Stronger dipoles produce more intense IR bands and weaker dipoles produce less intense IR bands (sometimes none). Bonds to Hydrogen (stretching wave numbers). C H. O. C C H. C H C H. 3000-3100. sp3 C-H 3300 2700-2760. sp3 C-H 2800-2860. 2850-3000 (see sp2 C-H bend aldehyde C-H.)

3 Sp3 C-H patterns below) (sp C-H bend 620) (two bands). H. O. C N C N R S H. R O H C O H. H H. 3100-3500 3100-3500 2550 -2620. primary NH2 secondary N-H 3200-3400 2500-3400 (very weak). (two bands) (one band). alcohol O-H acid O-H thiol S-H. amides = strong, amines = weak Z:\files\classes\ Spectroscopy \typical spectra Spectroscopy Data Tables 2. Carbonyl Highlights (stretching wave numbers). Aldehydes Ketones Esters Acids O O O O. C C C R' C H. R H R R R O R O. saturated = 1725 saturated = 1715 saturated = 1735 saturated = 1715. conjugated = 1690 conjugated = 1680 conjugated = 1720 conjugated = 1690. aromatic = 1700 aromatic = 1690 aromatic = 1720 aromatic = 1690. 6 atom ring = 1715 6 atom ring = 1735. 5 atom ring = 1745 5 atom ring = 1775. 4 atom ring = 1780 4 atom ring = 1840. 3 atom ring = 1850. Amides Anhydrides Acid Chlorides nitro O O O.

4 O. O. C C. C R N. R O R R Cl R NR2. saturated = 1650 saturated = 1760, 1820 saturated = 1800 O. conjugated = 1660 conjugated = 1725, 1785 conjugated = 1770. aromatic = 1725, 1785 aromatic = 1770 asymmetric = 1500-1600. aromatic = 1660 symmetric = 1300-1390. 6 atom ring = 1670 6 atom ring = 1750, 1800. 5 atom ring = 1700 5 atom ring = 1785, 1865. 4 atom ring = 1745 Very often there is a very weak C=O overtone at approximately 2 x ( 3400 cm-1). 3 atom ring = 1850 Sometimes this is mistaken for an OH or NH peak., sp2 C-H bend patterns for alkenes sp2 C-H bend patterns for aromatics absorption absorption alkene substitution descriptive frequencies (cm-1) aromatic substitution descriptive frequencies (cm-1). pattern alkene term pattern aromatic term due to sp2 CH bend due to sp2 CH bend R H. monosubstituted 985-1000 monosubstituted 690-710.

5 C C X. alkene 900-920 aromatic 730-770. H H. R R X. C C cis disubstituted 675-730. alkene (broad) 735-770. ortho disubstituted H H X aromatic R H. C C trans disubstituted 960-990. alkene X. H R. R H. meta disubstituted 680-725. X. geminal disubstituted 880-900 aromatic 750-810. C C. alkene 880-900 (sometimes). R H. R R. trisubstituted para disubstituted 790-840. C C 790-840 X X aromatic alkene R H. R R Aromatic compounds have characteristic weak overtone bands that show up between 1650-2000 cm-1). Some books provide C C tetrasubstituted alkene none pictures for comparison (not here). A strong C=O peak will R R cover up most of this region. Z:\files\classes\ Spectroscopy \typical spectra Spectroscopy Data Tables 3. units = cm-1. 4000 3500 3000 2500 2000 1700 1500 1400 1300 1200 1100 1000 900 800 700 600 500. sp3 C-H C C C=O alkene sp2 C-H.

6 Sp C-H bend stretch stretch stretch 3. sp C-H. thiol S-H bend mono sp2 C-H stretch C=N cis stretch C N stretch trans aldehyde C-H acyl C-O geminal stretch phenol C-O. C=C stretch tri alcohol O-H alkene stretch alkoxy C-O. carboxylic acid O-H C=C stretch aromatic aromatic sp2 C-H. stretch bend 1o N-H2 mono N-H bend stretch ortho 2o N-H nitro nitro meta stretch para 4000 3500 3000 2500 2000 1700 1500 1400 1300 1200 1100 1000 900 800 700 600 500. expansion of alkene & aromatic sp2 C-H bend region (units = cm-1). 1000 900 800 700 600 500. mono mono cis alkene sp2 C-H. trans geminal bend tri mono mono ortho aromatic sp2 C-H. bend meta meta meta para expansion of carbonyl (C=O) stretch region (units = cm-1). 1800 1750 1700 1650 1600. Saturated C=O lies at carboxylic acid C=O (also acid "OH") Conjugated C=O. higher cm-1 lies at lower cm-1.

7 C=O in samll rings ester C=O (also acyl C-O and alkoxy C-O). lies at higher cm-1. aldehyde C=O (also aldehyde C-H). ketone C=O (nothing special). amide C=O (low C=O, amide N-H). acid chloride C=O (high C=O, 1 peak). anhydride C=O anhydride C=O (high C=O, 2 peaks). Z:\files\classes\ Spectroscopy \typical spectra Spectroscopy Data Tables 4. IR Flowchart to determine functional groups in a compound (all values in cm-1). IR Spectrum has C=O band (1650-1800 cm-1) does not have C=O band very strong C C. C N. aldehydes O alkanes 1725-1740 (saturated) 2250 sp3 C-H stretch 2850-3000. 1660-1700 (unsaturated) nitriles C sharp, stronger 1460 & 1380. sometimes lost than alkynes, sp3 C-H bend 2860-2800 in sp3 CH peaks C N. C C not useful aldehyde C-H 2760-2700 a little lower (both weak) when conjugated alkenes sp2 C-H stretch 3000-3100. ketones alkynes 650-1000.

8 O 2150 sp2 C-H bend (see table for 1710-1720 (saturated) C C spectral patterns). 1680-1700 (unsaturated) (variable intensity). C 1715-1810 (rings: higher not present or weak when symmetrically 1600-1660. in small rings) substituted, a little lower when conjugated C C. weak or not present esters - rule of 3. O sp C-H stretch 3300 aromatics 1735-1750 (saturated) sharp, strong 1715-1740 (unsaturated) sp2 C-H stretch 3050-3150. C 1735-1820 (higher in small rings) sp C-H bend 620 690-900 (see table), acyl sp2 C-H bend overtone patterns 1150-1350 (acyl, strong) All IR values are approximate and have a range between 1660-2000. C O. alkoxy of possibilities depending on the molecular 1600 & 1480. C O. (1000-1150, alkoxy, medium) environment in which the functional group resides. C C can be weak Resonance often modifies a peak's position acids because of electron delocalization (C=O lower, O alcohols 1700-1730 (saturated) acyl C-O higher, etc.)

9 IR peaks are not 100%. reliable. Peaks tend to be stronger (more intense) alcohol 1715-1740 (unsaturated) 3600-3500. C when there is a large dipole associated with a O H. 1680-1700 (higher in small rings). vibration in the functional group and weaker in alkoxy 1000-1260. acyl less polar bonds (to the point of disappearing in C O (3o > 2o > 1o). C O 1210-1320 (acyl, strong) some completely symmetrical bonds). thiols acid 2550 (weak). 2400-3400, very broad thiol O H (overlaps C-H stretch) 2 S H (easy to overlook). Alkene sp C-H bending patterns amides amines O monosubstituted alkene (985-1000, 900-920) H. 3300 - 3500, two bands 1630-1680 (saturated) geminal disubstituted (960-990). 1745 (in 4 atom ring) N for 1o amines, one band C cis disubstituted (675-730) o N H for 2 amines, weaker trans disubstituted (880-900) 1o H 3350 & 3180, two bands H.

10 2o than in amides, trisubstituted (790-840). for 1o amides, tetrasubstituted (none, no sp2 C-H) N-H bend, 1550-1640, N one band for 2o amides, N H. stronger in amides than amines o 1 N H stronger than in amines, extra H. 2o overtone sometimes at 3100 N C 1000-1350. Aromatic sp2 C-H bending patterns (uncertain). ethers N H N-H bend, 1550-1640, monosubstituted (730-770, 690-710) 1120 (alphatic). stronger in amides than amines alkoxy ortho disubstituted (735-770) C O 1040 & 1250 (aromatic). acid chlorides meta disubstituted (880-900,sometimes, nitro compounds O 1800 (saturated) 750-810, 680-725). O. 1770 (unsaturated) para disubstituted (790-840) 1500-1600, asymmetric (strong). C Inductive pull of Cl increases the N 1300-1390, symmetric (medium). electron density between C and O. O. There are also weak overtone bands between anhydrides 1660 and 2000, but are not shown here.