sign in sign up
<<
Home , Aldehyde, Carbonyl group, Ester, Geminal, Ketone, Nh (digraph)

Beauchamp 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 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 may disappear, i.. a symmetrically substituted !). Infrared spectra are generally informative about what functional groups are present, but not always. The 1H and 13C NMR’ are often just as informative about functional groups, and sometimes even more so in this regard. 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 (stretching wave numbers)

sp3 - single bonds sp2 C-X single bonds

CN CO CO CC CC CN

1000-1350 1050-1150 1100-1350 not used not very useful alkoxy C- not very useful 1250 acyl and phenyl C-O sp2 C-X double bonds sp C-X triple bonds

CO CC CN CC CN 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 (stretching wave numbers)

CH O CCH CH 3000-3100 sp3 C- 3300 2700-2760 3 2800-2860 2850-3000 2 sp C-H (see sp C-H bend C-H 3 sp C-H patterns below) (sp C-H bend ≈ 620) (two bands) H O CN CN OH C OH R H H 3100-3500 3100-3500 2550 -2620 primary NH2 -H 3200-3400 2500-3400 (very weak) (two bands) (one band) O-H O-H S-H = strong, = weak

Z:\classes\spectroscopy\all spectra tables for web.DOC Beauchamp Spectroscopy Tables 2

Carbonyl Highlights (stretching wave numbers)

Aldehydes KetonesEsters 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 = 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 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 ν (≈3400 cm-1). 3 atom ring = 1850 Sometimes this is mistaken for an OH or NH peak.,

sp2 C-H bend patterns for sp2 C-H bend patterns for aromatics absorption absorption substitution descriptive frequencies (cm-1) aromatic substitution descriptive frequencies (cm-1) alkene term aromatic term pattern due to sp2 CH bend pattern due to sp2 CH bend R H monosubstituted 985-1000 monosubstituted CC X 690-710 alkene 900-920 aromatic 730-770 H H R R X

CC cis disubstituted 675-730 alkene (broad) ortho disubstituted 735-770 H H X aromatic R H

CC trans disubstituted 960-990 alkene X H R R H 680-725 X meta disubstituted aromatic 750-810 CC disubstituted 880-900 alkene 880-900 (sometimes) R H R R para disubstituted CC trisubstituted 790-840 alkene 790-840 X X aromatic R H R R Aromatic compounds have characteristic weak overtone bands that show up between 1650-2000 cm-1). Some books provide CC tetrasubstituted alkene none pictures for comparison (not here). A strong C=O peak will R R cover up most of this region.

Z:\classes\spectroscopy\all spectra tables for web.DOC Beauchamp Spectroscopy Tables 3

units = cm-1 4000 3500 3000 2500 2000 1700 1500 1400 1300 1200 1100 1000 900 800 700 600 500

2 3 alkene sp C-H sp C-H sp C-H CC C=O 3 bend stretch stretch stretch sp C-H thiol S-H bend mono sp2 C-H stretch C=N cis stretch CN stretch trans aldehyde C-H acyl C-O geminal stretch C-O C=C stretch tri alcohol O-H alkene stretch alkoxy C-O

C=C stretch O-H aromatic sp2 C-H stretch aromatic bend

1o N-H mono 2 N-H bend stretch ortho

2o N-H nitro nitro meta stretch para

4000 3500 3000 2500 2000 1700 15001400 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

2 ortho aromatic sp 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 C=O in samll rings C=O (also acyl C-O and alkoxy C-O) lies at higher cm-1 aldehyde C=O (also aldehyde C-H)

C=O (nothing special)

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:\classes\spectroscopy\all spectra tables for web.DOC Beauchamp Spectroscopy 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 CC

CN O 1725-1740 (saturated) 3 2850-3000 ≈ 2250 sp C-H stretch C 1660-1700 (unsaturated) sharp, stronger 3 1460 & 1380 sometimes lost than , sp C-H bend 3 CN 2860-2800 in sp CH peaks CC not useful aldehyde C-H 2760-2700 a little lower (both weak) when conjugated alkenes sp2 C-H stretch 3000-3100 alkynes 650-1000 O 2150 sp2 C-H bend (see table for 1710-1720 (saturated) CC spectral patterns) 1680-1700 (unsaturated) (variable intensity) C 1715-1810 (rings: higher not present or weak when symmetrically CC 1600-1660 in small rings) substituted, a little lower when conjugated weak or not present - 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), 2 overtone patterns acyl sp C-H bend All IR values are approximate and have a range between 1660-2000 CO 1150-1350 (acyl, strong) of possibilities depending on the molecular 1600 & 1480 alkoxy (1000-1150, alkoxy, medium) CO environment in which the functional group resides. CC can be weak often modifies a peak's position acids because of electron delocalization (C=O lower, O acyl C-O higher, etc.). IR peaks are not 100% 1700-1730 (saturated) alcohol reliable. Peaks tend to be stronger (more intense) 3600-3500 1715-1740 (unsaturated) OH C 1680-1700 (higher in small rings) when there is a large dipole associated with a vibration in the functional group and weaker in alkoxy 1000-1260 less polar bonds (to the point of disappearing in o o o acyl CO (3 > 2 > 1 ) CO 1210-1320 (acyl, strong) some completely symmetrical bonds). ≈ 2550 (weak) acid 2400-3400, very broad thiol (easy to overlook) OH (overlaps C-H stretch) Alkene sp2 C-H bending patterns SH amides amines O H monosubstituted alkene (985-1000, 900-920) 3300 - 3500, two bands 1630-1680 (saturated) geminal disubstituted (960-990) for 1o amines, one band C 1745 (in 4 atom ring) N cis disubstituted (675-730) for 2o amines, weaker 1o NH trans disubstituted (880-900) H o H 3350 & 3180, two bands 2 than in amides, o trisubstituted (790-840) for 1 amides, 2 N o tetrasubstituted (none, no sp C-H) NH N-H bend, 1550-1640, one band for 2 amides, stronger in amides than amines 1o NHstronger than in amines, extra H 2o overtone sometimes at 3100 NC 1000-1350 Aromatic sp2 C-H bending patterns (uncertain) NH N-H bend, 1550-1640, monosubstituted (730-770, 690-710) 1120 (alphatic) stronger in amides than amines alkoxy ortho disubstituted (735-770) CO 1040 & 1250 (aromatic) meta disubstituted (880-900,sometimes, acid chlorides nitro compounds 750-810, 680-725) O 1800 (saturated) 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. There are also weak overtone bands between O anhydrides 1660 and 2000, but are not shown here. You O can consult pictures of typical patterns in other carbon- bonds 1760 & 1820 (saturated) reference books. If there is a strong C=O band, 1725-1785 (unsaturated) they may be partially covered up. C two strong bands C X usually not acyl very useful CO 1150-1350 (acyl, strong) X = , Cl, Br, I

Z:\classes\spectroscopy\all spectra tables for web.DOC Beauchamp Spectroscopy Tables 5

deshielding side = less electron rich Typical 1H and 13C NMR values. shielding side = more electron rich (inductive & resonance) (inductive & resonance) typical proton chemical shifts N-H Carbon and/or heteroatoms without hydrogen do not appear here, but influence on any nearby protons 2 1 may be seen in the chemical shifts of the protons. alcohol O H 5 1 amide N-H 6 1 S C H thiols, 2.5 2.0 N C H amines 3.0 2.3 X C H X = F,Cl,Br,I allylic C-H 5 3 2.5 1.5 benzylic C-H thiol alkene C-H carbonyl alpha C-H SH + + carboxylic acid O-H 7 4 3 2 1.5 1.3 C-H 12 10 3.5 2.5 H alcohols simple sp3 C-H O C ethers aldehyde C-H aromatic C-H CH > CH > CH esters C H 2 3 + 10 9 8 6 5+ 3.3 3 2 2 0.5

12 11 10 9 8 7 PPM 6 5 4 3 2 1 0

typical carbon-13 chemical shifts halogen C F ≈ 80-95 Cl ≈ 45-70 Br ≈ 35-65 with & without H I ≈ 15-45 O 95 15 C N C R R ketones amines, amides no H with & without H

220+ 180 50 30 O O C R X with & without H carboxylic acids CC with & without H anhydrides 60 40 esters NC no H amides 90+ 70- S C acid chlorides 110 no H 125 thiols, sulfides with & without H 180 160 O C alcohols, 40 20 ethers, esters O with & without H C 80+ R H C CC 50 simple sp3 carbon aldehydes C > CH > CH2 > CH3 with H with & without H with & without H

+ - 210 180 160 100 60+ 0

240 220 200 180 160 140 PPM 120 100 80 60 40 20 0

Z:\classes\spectroscopy\all spectra tables for web.DOC Beauchamp Spectroscopy Tables 6

Calculation of chemical shifts for protons at sp3

Estimation of sp3 C-H chemical shifts with multiple parameters for protons within 3 C's of consideration. H

Cα Cβ Cγ α = directly attached substituent, use these values when the hydrogen and substituent are attached to the same carbon β = once removed substituent, use these values when the hydrogen and substituent are on adjacent () carbons γ = twice removed substituent, use these values when the hydrogen and substituent have a 1,3 substitution pattern

Starting value and equations for CH 's X = substituent α β γ 3 R- () 0.0 0.0 0.0 α R2C=CR- (alkenyl) 0.8 0.2 0.1 δ CH3 = 0.9 + α H3C RCC- (alkynyl) 0.9 0.3 0.1 Ar- (aromatic) 1.4 0.4 0.1 F- (fluoro) 3.2 0.5 0.2 δ CH3 = 0.9 + ∑(β + γ) H CC C Cl- (chloro) 2.2 0.5 0.2 3 β γ Br- (bromo) 2.1 0.7 0.2 I- (iodo) 2.0 0.9 0.1 ∑ is the summation symbol for all substituents considered HO- (alcohol) 2.3 0.3 0.1 RO- () 2.1 0.3 0.1 epoxide 1.5 0.4 0.1 Starting value and equation for CH2's R2C=CRO- (alkenyl ether) 2.5 0.4 0.2 ArO- (aromatic ether) 2.8 0.5 0.3 In a similar manner we can calculate chemical shifts RCO - (ester, side) 2.8 0.5 0.1 2 for methylenes (CH2) using the following formula ArCO2- (aromatic ester, oxygen side) 3.1 0.5 0.2 ArSO - (aromatic , oxygen) 2.8 0.4 0.0 H 3 δ CH2 = 1.2 + ∑(α +β + γ) H2N- (amine ) 1.5 0.2 0.1 H Cα Cβ Cγ RCONH- (amide nitrogen) 2.1 0.3 0.1 O N- (nitro) 3.2 0.8 0.1 2 ∑ is the summation symbol for all substituents considered HS- (thiol, ) 1.3 0.4 0.1 RS- (, sulfur) 1.3 0.4 0.1 Starting value and equation for CH's OHC- (aldehyde) 1.1 0.4 0.1 RCO- (ketone) 1.2 0.3 0.0 ArCO- (aromatic ketone) 1.7 0.3 0.1 In a similar manner we can calculate chemical shifts for methines (CH) using the following formula HO2C- (carboxylic acid) 1.1 0.3 0.1 RO2C- (ester, carbon side) 1.1 0.3 0.1 H H NOC- (amide, carbon side) 1.0 0.3 0.1 δ CH = 1.5 + ∑(α +β + γ) 2 C C C ClOC- (acid chloride) 1.8 0.4 0.1 α β γ NC- () 1.1 0.4 0.2 RSO- () 1.6 0.5 0.3 ∑ is the summation symbol for all substituents considered RSO2- () 1.8 0.5 0.3 a. methine . methylene

HO CH2 CH3 . methyl O CH N

H2C H H3C H2C c. methyl

e. methylene f. methylene

a. methyl = 0.9 + (1.5)α + (0.1)γ = 2.5 ppm d. methyl = 0.9 + (0.1)α = 1.0 ppm actual = 2.6 actual = 1.0

b. methylene = 1.2 + (1.5)α + (0.4)β + (0.3)β = 3.4 ppm e. methylene = 1.2 + (0.3)α = 1.5 ppm actual = 3.0 and 3.2 actual = 1.7

c. methine = 1.5 + (1.4)α + (2.3)α + (0.2)β = 5.4 ppm f. methylene = 1.2. + (1.7)α = 2.9 ppm actual = 5.2 actual = 2.9

Z:\classes\spectroscopy\all spectra tables for web.DOC Beauchamp Spectroscopy Tables 7

Estimated chemical shifts for protons at alkene sp2 carbons

Substituent α geminal α cis α trans Substitution relative to calculated "H" cis H- 0.0 0.0 0.0 H Hydrogen CC R- 0.5 -0.2 -0.3 trans gem Alkyl C6H5CH2- 0.7 -0.2 -0.2 δ(ppm) = 5.2 + α gem + α cis + α trans Benzyl X-CH2- 0.7 0.1 0.0 Halomethyl Example Calculation (H)/ROCH2- 0.6 0.0 0.0 alkoxymethyl gem (H)2/R2NCH2- 0.6 -0.1 -0.1 H trans aminomethyl C H RCOCH2- 0.7 -0.1 -0.1 C α-keto H NCCH2- 0.7 -0.1 -0.1 CH3O cis α-cyano R2C=CR- 1.2 0.0 0.0 Alkenyl δ gem = 5.2 + 1.4 = 6.6 C6H5- 1.4 0.4 -0.1 actual = 6.6 Phenyl F- 1.5 -0.4 -1.0 δ trans = 5.2 - 0.1 = 5.1 Fluoro actual = 5.1 Cl- 1.1 0.2 0.1 δ cis = 5.2 + 0.4 = 5.7 Chloro actual = 5.6 Br- 1.1 0.4 0.6 Bromo I- 1.1 0.8 0.9 c d e Iodo b H H HH RO- 1.2 -1.1 -1.2 C C C C akoxy (ether) a H OC H f RCO2- 2.1 -0.4 -0.6 O-ester O (H) /R N- 0.8 -1.3 -1.2 2 2 δa = 5.2 + (-0.4) = 4.8 N-amino actual = 4.9 ( = 14, 1.6 Hz) RCONH- 2.1 -0.6 -0.7 N-amide δb = 5.2 + (-0.6) = 4.6 actual = 4.6 (J = 6, 1.6 Hz) O2N- 1.9 1.3 0.6 Nitro δc = 5.2 + 2.1 = 7.3 RS- 1.1 -0.3 -0.1 actual = 7.4 (J = 14, 6 Hz) Thiol OHC- 1.0 1.0 1.2 δd = 5.2 + 0.8 = 6.0 Aldehyde actual = 6.2 (J = 18, 11 Hz) ROC- 1.1 0.9 0.7 δe = 5.2 + 0.5 = 5.7 Ketone actual = 5.8 (J = 11, 1.4 Hz) HO2C- 0.8 1.0. 03 C-acid δf = 5.2 + 1.0 = 6.2 actual = 6.4 (J = 18, 1.4 Hz) RO2C- 0.8 1.0 0.5 C-ester H2NOC- 0.4 1.0 0.5 C-amide NC- 0.3 0.8 0.6 Nitrile

Z:\classes\spectroscopy\all spectra tables for web.DOC Beauchamp Spectroscopy Tables 8

Estimated chemical shifts for protons at aromatic sp2 carbons Substitution relative to calculated "H" Substituent α ortho α meta α para meta ortho H- 0.0 0.0 0.0 Hydrogen para H CH3- -0.2 -0.1 -0.2 Methyl ClCH - 0.0 0.0 0.0 2 meta ortho Cholromethyl Cl3C- 0.6 0.1 0.1 δ(ppm) = 7.3 + α ortho + α meta + α para Halomethyl HOCH2- -0.1 -0.1 -0.1 Hydroxymethyl Example Calculation R2C=CR- 0.1 0.0 -0.1 Alkenyl 2 C H - 1.4 0.4 -0.1 H 6 5 1 Phenyl 3 CH3O H 5 F- -0.3 0.0 -0.2 H Fluoro H 6 Cl- 0.0 0.0 -0.1 HCH Chloro 2 2 4 Br- 0.2 -0.1 0.0 H H Bromo 3 7 I- 0.4 -0.2 0.9 Iodo 1. δ (CH3) = 0.9 + 2.8 = 3.7 HO- -0.6 -0.1 -0.5 actual = 3.8 Hydroxy RO- -0.5 -0.1 -0.4 2. δ (2) = 7.3 + (-0.5) ortho + (-0.1) para = 6.7 Alkoxy actual = 6.8 RCO2- -0.3 0.0 -0.1 O-ester 3. δ (3) = 7.3 + (-0.2) ortho + (-0.4) para = 6.7 (H)2/R2N- -0.8 -0.2 -0.7 actual = 7.1 N-amino RCONH- 0.1 -0.1 -0.3 4. δ (CH2) = 1.2 + (0.8)α + (1.4)α = 3.4 N-amide actual = 3.3 O2N- 1.0 0.3 0.4 Nitro 5. δ (5) = 5.2 + (0.7) gem = 5.9 RS- -0.1 -0.1 -0.2 actual = 5.9 thiol/sulfide OHC- 0.6 0.2 0.3 6. δ (6) = 5.2 + (-0.2) = 5.0 Aldehyde trans ROC- 0.6 0.1 0.2 actual = 5.1 Ketone HO2C- 0.9 0.2 0.3 7. δ (7) = 5.2 + (-0.2) cis = 5.0 C-acid actual = 5.1 RO2C- 0.7 0.1 0.2 C-ester H2NOC- 0.6 0.1 0.2 C-amide NC- 0.4 0.2 0.3 Nitrile

Z:\classes\spectroscopy\all spectra tables for web.DOC Beauchamp Spectroscopy Tables 9

Real Examples of Combination Effects on Chemical Shifts π bond anisotropy 0.8 shielded σ bond example too

(CH2) 0.8, shielded H shielding cone from σ bond CH2 2.6 H deshielded H 7.2 1.5

and π bond 10-12 15, hydrogen H bonded O O H O O O C H 9.5 C C C C H C C CH OH O hydrogen 3 3 bonding H electronegative substituent and distance from protons

OCH2CH2CH2CH2CH3 CH3 Cl CH3CH2 Cl CH3CH2CH2 Cl CH3CH2CH2CH2 Cl CH3CH2 R

3.6 1.5 1.3 1.3 0.9 3.0 1.3 1.0 0.9 0.9 multiple substituents

CH4 CH3Cl CH2Cl2 CHCl3 CCl4

0.2 ∆ = 2.8 3.0 ∆ = 2.3 5.3 ∆ = 1.9 7.2 ∆ = ? ? (oops)

substituents at methyl (CH3), methylene (CH2) and methine (CH) O O O CH Cl CH CH Cl (CH ) CHCl C C C 3 3 2 3 2 H3CPhH3CH2CPh(H3C)2CH Ph

3.0 3.5 4.1 2.6 3.0 3.5

alkene substituent resonance and inductive effects O 0.9 1.4 2.0 O 3.7 4.2 4.9 H H 3.8 6.4 CH3CH2CH2 H 5.0 H C O H C O H CH3O C H 2 CC H C H3C CC CC CC 3 CC H H 1.3 2.1 H H H H H H H H 5.3 5.8 4.9 6.1 5.8 6.5 4.0 7.3 4.6 aromatic resonance and inductive effects H H 7.3 6.6 7.1 8.2 7.5 H H H H H H H H O O HH 6.7 7.7 NHNH H2NHH2NH O O H H π bond anisotropy H H H H H H H H produces deshielding Extra electron density via resonance produces Withdrawal of electron density via resonance effect on aromatic shielding effect on aromatic protons, especially produces deshielding effect on aromatic protons, protons. at ortho/para positions. especially at ortho/para positions. sp C-H H O RO H alcohol H = 1-5 R2NHamine H = 1-5 enol H = 10-17 H CHC 2.4 CC ArO H phenol H = 4-10 O O R CHC 1.9 RS H amide H = 5-8 thiol H = 1-2.5 R C R C ArO H Ar CHC 3.0 aromatic thiol H = 3-4 NH2 OHacid H = 10-13

Z:\classes\spectroscopy\all spectra tables for web.DOC Beauchamp Spectroscopy Tables 10

Proton chemical shifts of hydrogen on sp3 carbons depend on two main factors (electronegativity and anisotropy). All values listed below are only approximate and have a small plus or minus range about the listed value. All things being equal, methine protons (CH) have greater chemical shifts than methylene protons (CH2) which have greater chemical shifts than methyl protons (CH3).

H H CH CH CH H δ 1.5 ppm δ 1.2 ppm δ 0.9 ppm methine protons methylene protons methyl protons Chemical shifts in an only "" environment.

1. sp3 C-H Electronegative in the vicinity of hydrogen deshield protons and produce a larger chemical shift. If the electronegative atom is in resonance with an adjacent pi system that further withdraws electron density, the chemical shift is increased. a. next to a halogen H H H H CF CCl CBr CI

δ 4.1 - 4.7 ppm δ 3.1 - 3.7 ppm δ 3.0 - 3.6 ppm δ 2.9 - 3.5 ppm fluoro alkanes chloro alkanes bromo alkanes iodo alkanes b. next to a oxygen O O H H H O H H C R C COH COR CO C CO CO H δ 3.1 - 3.7 ppm δ 3.0 - 3.6 ppm δ 3.7 - 4.3 ppm δ 2.5 - 3.2 ppm δ 3.7 - 4.3 ppm δ 4.0 - 4.6 ppm alcohol alkyl ether alkyl ester aromatic ester aromatic ether epoxide ether (resonance withdrawal) (oxygen side) (oxygen side) (resonance withdrawal) (resonance withdrawal) c. next to a sulfur or nitrogen O H H H H C CSH CSR CN CN

δ 2.2 - 2.8 ppm δ 2.2 - 2.8 ppm δ 2.3 - 3.1 ppm δ 3.0 - 3.6 ppm thiol alkyl ether amines (resonance withdrawal) amides

2. sp3 C-H Pi bonds in the vicinity of hydrogen also deshield protons via pi bond anisotropy and produce a larger chemical shift. The closer the sp3 C-H is to the pi bond the greater chemical shift observed. When an electronegative atom is part of the pi bond, the chemical shift also increases.

H O H O H O H O CC CC CC CN Cl O δ 1.9 - 2.7 ppm aldehydes, ketones, δ 2.6 - 3.3 ppm δ 2.7 - 3.4 ppm δ 2.7 - 3.4 ppm carboxylic acids, amides, aromatic ketones acid chlorides nitro compounds alkyl ester (oxygen side) (resonance withdrawal) (resonance withdrawal) (resonance withdrawal)

H H H C C CC CC C

δ 1.8 - 2.4 ppm δ 2.3 - 2.9 ppm propargylic protons δ 1.7 - 2.3 ppm allylic protons benzylic protons

Z:\classes\spectroscopy\all spectra tables for web.DOC Beauchamp Spectroscopy Tables 11

3. sp2 C-H at the side of a pi bond are deshielded even more than above via pi bond anisotropy. An aldehyde produces the largest effect due to the electronegative oxygen, followed by an aromatic ring, followed by alkenes and finally terminal alkynes. (One sp C-H)

δ 4.0 - 4.6 ppm alkene C-H H H δ 5.5 - 6.5 ppm H H H δ 5.0 ppm O C H O C H C H C H C H CC CC RO C RO C RC H H H H H δ 6.0 - 6.3 ppm δ 6.4 - 7.4 ppm 5.7 ppm δ vinylic protons (resonance vinylic protons (resonance donation simple vinylic protons and inductive withdrawal) and inductive withdrawal) aromatic C-H δ 7.9 - 8.3 ppm δ 6.7 - 7.0 ppm δ 6.5 - 7.0 ppm δ 7.1 - 7.3 ppm H H H H O C O N R simple aromatic protons aromatic protons (resonance aromatic protons (resonance donation and inductive withdrawal) and inductive withdrawal) aldehyde C-H alkyne C-H O C CHC H δ 9 - 10 ppm δ 1.9 - 3.2 ppm aldehydes terminal alkyne protons

4. There are several kinds of hydrogen attached to heteroatoms. Some of these are listed below. Often these hydrogens do not follow the N+1 rule because they exchange via acid/ proton exchanges and are not next to neighbor protons long enough to allow coupling to be observed. They are often observed as broad singlets (sometimes so broad they are not easily seen in the spectra). If the exchange rate is very fast among the exchangeable protons on the NMR time scale, all of the exchangeable protons may appear together at a single, averaged chemical shift.

O O O O O H H H N C C H OH NH δ 1 - 5 ppm δ 1 - 2 ppm δ 10 - 12 ppm alcohols δ 7 - 15 ppm δ 1 - 6 ppm amines carboxylic acids phenol and amides enol protons

Z:\classes\spectroscopy\all spectra tables for web.DOC Beauchamp Spectroscopy Tables 12

When carbons are decoupled from their attached hydrogens they all appear as singlets (as if there were no hydrogen neighbors). When carbons are coupled to their hydrogens, carbons follow the N+1 rule. Methyls appear as quartets = , methylenes appear as triplets = , methines appear as doublets = d, and carbons without hydrogen appear as singlets = s. Carbon chemical shifts are spread out over a larger range than proton chemical shifts (they are more dispersed). It is less likely that two different carbon shifts will fall on top of one another. However, the relative positions of various types of proton and carbon shifts have many parallel trends (shielded protons tend to be on shielded carbons, etc.)

CH2 CH C Simple alkane CH3 carbons δ 0 - 30 ppm δ 20 - 40 ppm δ 30 - 50 ppm δ 30 - 60 ppm (q) (t) (d) (s)

CH2 sp3 carbon CH3 CH C next to oxygen δ 50 - 60 ppm δ 55 - 80 ppm δ 60 - 80 ppm δ 70 - 90 ppm (q) (t) (d) (s)

CH2 sp3 carbon CH3 CH C next to nitrogen δ 10 - 50 ppm δ 35 - 55 ppm δ 50 - 70 ppm δ 50 - 70 ppm (q) (t) (d) (s)

CH sp3 carbon next to 2 CH C bromine or 25 - 50 ppm δ δ 60 - 80 ppm δ 60 - 80 ppm (t) (d) (s)

sp carbon (alkynes) CC sp carbon (nitriles) CN δ 70 - 90 ppm δ 110 - 125 ppm

sp2 carbon (alkenes CX and aromatics) CH CH CX

δ 100 - 140 ppm δ 140 - 160+ ppm 2 simple sp2 carbon sp carbon attached to an electronegative atom (X = oxygen, nitrogen, halogen) or C carbon resonance donation moves δ lower, β conjugated with a resonance withdrawal moves δ higher

O O O C C C X H R δ 160 - 180 ppm δ 190 - 210 ppm δ 190 - 220 ppm carboxyl carbons aldehyde carbons, lower ketone carbons, lower (acids, esters, amides) values when conjugated values when conjugated (s) (d) (s)

Z:\classes\spectroscopy\all spectra tables for web.DOC Beauchamp Spectroscopy Tables 13

1. One nearest neighbor proton increasing δ one neighbor increasing ∆E (ν, B ) H1 proton = Ha o Ha CC observed the ratio of these perturbation(s) by proton two populations neighbor proton(s) is about 50/50 (or 1:1) ∆Eto flip proton H1 ∆E2 (observed) Bo ∆E1 (observed) J1a 1 1 Protons in this environment have a small cancellation Protons in this environment have a small H1 H1 of the external magnetic field, Bo, and produce a additional increment added to the external smaller energy transition by that tiny amount. CC CC magnetic field, Bo, and produce a higher energy transition by that tiny amount.

J = coupling constant N + 1 rule (N = # neighbors) small difference in energy due to differing J (Hz) # peaks = N + 1 = 1 + 1 = 2 peaks neighbor's spin (in Hz)

δ (ppm) 2. Two nearest neighbor protons (both on same carbon or one each on separate carbons) the ratio of these two neighbor four populations H1 protons Ha is about 1:2:1 CCH H observed b 1 ∆E proton ∆Eto flip proton 1 ∆E2 J1a ∆E3

Bo J1b J1b two equal energy 1 2 1 H two neighbor protons are like 1 populations here two small magnets that can be CC arranged four possible ways N + 1 rule (N = # neighbors) (similar to flipping a coin twice) J (Hz) J (Hz) # peaks = N + 1 = 2 + 1 = 3 peaks

δ (ppm) 3. Three nearest neighbor protons (on same carbon, or two on one and one on another, or one each on separate carbons)

three neighbor the ratio of these H1 protons eight populations Ha is about 1:3:3:1 CCH observed b H1 proton Hc ∆E ∆E 1 to flip proton ∆E2 J1a ∆E3 ∆E4 Bo J1b J1b

H three neighbor protons are like 1 J1c J1c J1c three small magnets that can be three equal energy 1 3 31 CC arranged eight possible ways populations at each (similar to flipping a coin thrice) of middle transitions

N + 1 rule (N = # neighbors) J (Hz) J (Hz) J (Hz) # peaks = N + 1 = 3 + 1 = 4 peaks

δ (ppm)

Z:\classes\spectroscopy\all spectra tables for web.DOC Beauchamp Spectroscopy Tables 14

Multiplets when the N + 1 rule works (all J values are equal).

1 peak = 100% s = singlet 1 1 peak = 50% d = doublet 11 1 peak = 25% t = triplet 121 1 peak = 12% relative sizes of q = quartet 13 3 1 1 peak = 6% peaks in multiplets qnt = quintet 146 4 1 1 peak = 3% sex = sextet 1510 10 51 1 peak = 1.5% sep = septet 1615 20 15 6 1 o = octet 1 peak = 0.8% 1 7 21 35 35 21 7 1

Combinations or these are possible.

dd = doublet of doublets ddd = doublet of doublet of doublets dddd = doublet of doublet of doublet of doublets dt = doublet of triplets td = triplet of doublets

etc.

Z:\classes\spectroscopy\all spectra tables for web.DOC Beauchamp Spectroscopy Tables 15

Typical Coupling Constants Range Typical Range Typical

Ha Ha C Hb 0-3 Hz 1 Hz 0-30 Hz 14 Hz C CC Hb geminal protons - can have different chemical shifts cis / allylic coupling, and split one another if they are diastereotopic notice through 4 bonds Range Typical Range Typical Ha Ha Hb 6-8 Hz 7 Hz CC 0-3 Hz 1 Hz C C C Hb

vicinal protons are on adjacent atoms, when freely trans / allylic coupling, rotating coupling averages out to about 7 Hz notice through 4 bonds Range Typical Range Typical θ = dihedral H H C C a b angle CC C C H 0-12 Hz 7 Hz 9-13 Hz 10 Hz H H depends on dihedral a b 2 H angle, see plot of sp vicinal coupling Karplus equation (different π bonds)

Range Typical Range Typical H H a b Ha H 0-1 Hz 0 Hz b 1-3 Hz 2 Hz C CC C C O protons rarely couple through 4 chemical bonds sp3 vicinal aldehyde coupling unless in a special, rigid shapes (i.e. coupling) Range Typical Range Typical

H H H a 0-3 Hz 2 Hz a b 5-8 Hz 6 Hz CC CC

Hb C O 2 sp2 geminal coupling sp vicinal aldehyde coupling

Range Typical Range Typical H H a b H CC 5-11 Hz 10 Hz a 2-3 Hz 2 Hz C CCHb

sp2 cis (acylic) coupling (always sp / propargylic coupling smaller than the trans isomer) notice through 4 bonds Range Typical Range Typical Ha CC Ha Hb 11-19 Hz 17 Hz 2-3 Hz 3 Hz Hb C CCC

2 sp trans coupling (always bis-propargylic coupling larger than the cis isomer) notice through 5 bonds

Range Typical ortho, meta and H Range Typical Ha para coupling to Hortho CC 4-10 Hz 7 Hz this proton ortho 6-10 Hz 9 Hz CHb meta 2-3 Hz 2 Hz Hmeta para 0-1 Hz 0 Hz 2 3 sp / sp vicinal coupling Hpara When J values are less than 1 Hz, it is often difficult to resolve them and a peak may merely appear wider and shorter.

Z:\classes\spectroscopy\all spectra tables for web.DOC