IR NMR Table - chemistry PDF

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Summary

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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, i.e. 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. 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) sp 3 C-X single bonds

sp 2 C-X single bonds C

C

C

N

C

O C

C

1050-1150 alkoxy C-O

1000-1350 not very useful

not used

C

not very useful

sp 2 C-X double bonds

C

1600-1680

1100-1350 acyl and phenyl C-O

1250

O C

C

C

C

N

1640-1810 expanded table on next page

1640-1690

2100-2250

N

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

C

H

H

C

3000-3100 sp3 C-H (see sp2 C-H bend patterns below)

2850-3000 sp 3 C-H

H

2700-2760 2800-2860 aldehyde C-H (two bands)

3300 sp 3 C-H (sp C-H bend ≈ 620)

H O C

N

C

N

R

H

H

3100-3500 primary NH2 (two bands)

3100-3500 secondary N-H (one band)

amides = strong, amines = weak

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O

H

C

O

H

3200-3400

2500-3400

alcohol O-H

acid O-H

R

O

N

sp C-X triple bonds C

C

C

S

H

2550 -2620 (very weak) thiol S-H

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Carbonyl Highlights (stretching wave numbers) Aldehydes

Ketones

Esters

O

O

O

C H

R

saturated = 1725 conjugated = 1690 aromatic = 1700

Anhydrides O

O

C O

R

R

saturated = 1760, 1820 conjugated = 1725, 1785 aromatic = 1725, 1785 6 atom ring = 1750, 1800 5 atom ring = 1785, 1865

Cl

saturated = 1800 conjugated = 1770 aromatic = 1770

R

N O

asymmetric = 1500-1600 symmetric = 1300-1390

Very often there is a very weak C=O overtone at approximately 2 x ν (≈3400 cm-1). Sometimes this is mistaken for an OH or NH peak.,

sp2 C-H bend patterns for alkenes descriptive alkene term

sp2 C-H bend patterns for aromatics

absorption frequencies (cm-1 ) due to sp 2 CH bend

descriptive aromatic term

aromatic substitution pattern

absorption frequencies (cm-1) due to sp2 CH bend

H C

C

H

H

R

R C

C

H

H

R

H C

monosubstituted alkene

985-1000 900-920

cis disubstituted alkene

675-730 (broad)

monosubstituted aromatic

X

ortho disubstituted aromatic

X

960-990

C

R

H

R

R C

C

R

H

R

R C

C

geminal disubstituted alkene

880-900

trisubstituted alkene

790-840

tetrasubstituted alkene R

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none

735-770

X

R H C

690-710 730-770

X

trans disubstituted alkene

C

H R

R

nitro

O

C

saturated = 1650 conjugated = 1660 aromatic = 1660 6 atom ring = 1670 5 atom ring = 1700 4 atom ring = 1745 3 atom ring = 1850

R

saturated = 1715 conjugated = 1690 aromatic = 1690

Acid Chlorides

O

R

NR 2

alkene substitution pattern

O

O

C R

R

O

saturated = 1735 conjugated = 1720 aromatic = 1720 6 atom ring = 1735 5 atom ring = 1775 4 atom ring = 1840

saturated = 1715 conjugated = 1680 aromatic = 1690 6 atom ring = 1715 5 atom ring = 1745 4 atom ring = 1780 3 atom ring = 1850

H

C

R'

R

R

Amides

O

C

C

R

Acids

X

X

X

meta disubstituted aromatic

para disubstituted aromatic

680-725 750-810 880-900 (sometimes)

790-840

Aromatic compounds have characteristic weak overtone bands that show up between 1650-2000 cm-1). Some books provide pictures for comparison (not here). A strong C=O peak will cover up most of this region.

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units = cm-1

sp C-H stretch

2000

2500

3000

3500

4000

1700

C C

sp3 C-H stretch thiol S-H stretch

sp 2 C-H stretch

C=O stretch

C N

mono cis

trans geminal

acyl C-O phenol C-O

tri

C=C stretch aromatic

1o N-H 2 stretch

aromatic sp2 C-H bend mono

N-H bend

ortho

2o N-H stretch

nitro

meta

nitro

para 3000

2500

1700

2000

1500 1400 1300 1200 1100 1000 900

expansion of alkene & aromatic sp2 C-H bend region (units = cm-1) 700 600 800

900

mono

C-H bend

alkoxy C-O

carboxylic acid O-H stretch

1000

600 500

alkene sp2 C-H bend

sp3

C=C stretch alkene

alcohol O-H stretch

3500

1000 900 800 700

C=N stretch

aldehyde C-H stretch

4000

1500 1400 1300 1200 1100

800 700

600 500

500

mono

alkene sp2 C-H bend

cis trans geminal

tri

mono

mono

aromatic sp2 C-H bend

ortho meta

meta

meta

para

expansion of carbonyl (C=O) stretch region (units = cm-1) 1750 1700

1800

carboxylic acid C=O (also acid "OH")

Saturated C=O lies at higher cm-1 C=O in samll rings lies at higher cm-1

1650

ester C=O (also acyl C-O and alkoxy C-O) aldehyde C=O (also aldehyde C-H) ketone C=O (nothing special)

acid chloride C=O (high C=O, 1 peak) anhydride C=O

anhydride C=O (high C=O, 2 peaks)

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amide C=O (low C=O, amide N-H)

1600

Conjugated C=O lies at lower cm-1

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IR Flowchart to determine functional groups in a compound (all values in cm-1). IR Spectrum

has C=O band (1650-1800 cm-1 ) very strong

C

C

C

N

does not have C=O band

aldehydes

alkanes

O

1725-1740 (saturated) 1660-1700 (unsaturated) C sometimes lost 2860-2800 in sp 3 CH peaks 2760-2700 aldehyde C-H (both weak) ketones 1710-1720 (saturated) 1680-1700 (unsaturated) 1715-1810 (rings: higher in small rings)

C

esters - rule of 3 O

1735-1750 (saturated) 1715-1740 (unsaturated) 1735-1820 (higher in small rings)

C

acyl

1150-1350 (acyl, strong)

O

alkoxy C

(1000-1150, alkoxy, medium)

O

acids O

1700-1730 (saturated) 1715-1740 (unsaturated) 1680-1700 (higher in small rings)

C

acyl C

O

1210-1320 (acyl, strong)

H

2400-3400, very broad (overlaps C-H stretch)

acid O

amides O

1630-1680 (saturated) 1745 (in 4 atom ring)

C H N

1o

C

N

≈ 2250 sharp, stronger than alkynes,

sp3 C-H stretch

2850-3000

sp3

C-H bend

1460 & 1380

C

not useful

C

a little lower when conjugated

alkenes sp 2 C-H stretch

3000-3100

alkynes

O

C

nitriles

N H

N

2o

H

3350 & 3180, two bands for 1o amides, one band for 2o amides, H stronger than in amines, extra overtone sometimes at 3100

N-H bend, 1550-1640, stronger in amides than amines

acid chlorides O

1800 (saturated) 1770 (unsaturated)

C

Inductive pull of Cl increases the electron density between C and O.

anhydrides O

1760 & 1820 (saturated) 1725-1785 (unsaturated) two strong bands

C

2150 C C (variable intensity) not present or weak when symmetrically substituted, a little lower when conjugated sp C-H stretch sp C-H bend

3300 sharp, strong

650-1000 (see table for spectral patterns)

sp 2 C-H bend C

1600-1660 weak or not present

C

aromatics sp2 C-H stretch

3050-3150 690-900 (see table), overtone patterns between 1660-2000

620

sp2 C-H bend All IR values are approximate and have a range of possibilities depending on the molecular environment in which the functional group resides. C C Resonance often modifies a peak's position because of electron delocalization (C=O lower, alcohols acyl C-O higher, etc.). IR peaks are not 100% alcohol reliable. Peaks tend to be stronger (more intense) O H when there is a large dipole associated with a vibration in the functional group and weaker in alkoxy less polar bonds (to the point of disappearing in C O some completely symmetrical bonds). thiols thiol S H Alkene sp2 C-H bending patterns amines H monosubstituted alkene (985-1000, 900-920) geminal disubstituted (960-990) N cis disubstituted (675-730) N o 1 trans disubstituted (880-900) H 2o trisubstituted (790-840) tetrasubstituted (none, no sp2 C-H) N H

Aromatic sp2 C-H bending patterns monosubstituted (730-770, 690-710) ortho disubstituted (735-770) meta disubstituted (880-900,sometimes, 750-810, 680-725) para disubstituted (790-840)

N

3600-3500 1000-1260 (3o > 2o > 1o) ≈ 2550 (weak) (easy to overlook)

3300 - 3500, two bands for 1o amines, one band o H for 2 amines, weaker than in amides, N-H bend, 1550-1640, stronger in amides than amines 1000-1350 (uncertain)

C

ethers alkoxy C

1120 (alphatic) 1040 & 1250 (aromatic)

O

nitro compounds O

1500-1600, asymmetric (strong) 1300-1390, symmetric (medium)

N

There are also weak overtone bands between 1660 and 2000, but are not shown here. You can consult pictures of typical patterns in other reference books. If there is a strong C=O band, they may be partially covered up.

1600 & 1480 can be weak

O

carbon-halogen bonds

C

X

acyl C

O

1150-1350 (acyl, strong) X = F, Cl, Br, I

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usually not very useful

Be a uc ha mp

Sp e c tro sc o p y Ta b le s Typical 1H and

deshielding side = less electron rich (inductive & resonance)

13C

5

NMR chemical shift values.

shielding side = more electron rich (inductive & resonance)

typical proton chemical shifts amine N-H

Carbon and/or heteroatoms without hydrogen do not appear here, but influence on any nearby protons may be seen in the chemical shifts of the protons.

2 alcohol

O

1

H

5

1 amide N-H

6

1 S C H thiols, sulfides

2.5 N

3.0

X C H X = F,Cl,Br,I

3

7+

3+

4

10

10 10

11

1.5

2

1.5 1.3

aromatic C-H

9

8+

9

8

7

PPM

alcohols ethers esters

C

5+

6

2

2

3

4

halogen

0.5

2

1

15

95

C

N C

R ketones

amines, amides with & without H

no H 220 +

0

F ≈ 80-95 Cl ≈ 45-70 Br ≈ 35-65 I ≈ 15-45

C

with & without H O

simple sp3 C-H CH > CH2 > CH 3

H

3.3 3 5

6

2.5

3.5

H O C

typical carbon-13 chemical shifts

R

thiol SH

epoxide C-H

aldehyde C-H

12

2.5

benzylic C-H carbonyl alpha C-H

alkene C-H

12

2.3 allylic C-H

5

carboxylic acid O-H

2.0

C H amines

180

50 O

O

30

C R

180

C C with & without H

N C no H

90 +

220

200

S

C

thiols, sulfides with & without H

160

O

C

alcohols, ethers, esters

40

20

with & without H C

H

aldehydes with H

240

40

110

125

C

210

60

70-

O R

epoxides with & without H

X

carboxylic acids anhydrides esters amides acid chlorides no H

C

80

C

+

50

with & without H 180

180

+

100 -

160

160

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140 PPM 120

100

simple sp3 carbon C > CH > CH 2 > CH3 with & without H

60 +

80

60

0

40

20

0

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Calculation of chemical shifts for protons at sp3 carbons H C α C β Cγ

Estimation of sp3 C-H chemical shifts with multiple substituent parameters for protons within 3 C's of consideration. 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 (vicinal) carbons γ = twice removed substituent, use these values when the hydrogen and substituent have a 1,3 substitution pattern

X = substituent R- (alkyl) R2C=CR- (alkenyl) RCC- (alkynyl) Ar- (aromatic) F- (fluoro) Cl- (chloro) Br- (bromo) I- (iodo) HO- (alcohol) RO- (ether) epoxide R2C=CRO- (alkenyl ether) ArO- (aromatic ether) RCO2- (ester, oxygen side) ArCO2- (aromatic ester, oxygen side) ArSO3- (aromatic sulfonate, oxygen) H2N- (amine nitrogen) RCONH- (amide nitrogen) O2N- (nitro) HS- (thiol, sulfur) RS- (sulfide, sulfur) OHC- (aldehyde) RCO- (ketone) ArCO- (aromatic ketone) HO2C- (carboxylic acid) RO2C- (ester, carbon side) H2NOC- (amide, carbon side) ClOC- (acid chloride) NC- (nitrile) RSO- (sulfoxide) RSO2- (sulfone)

α 0.0 0.8 0.9 1.4 3.2 2.2 2.1 2.0 2.3 2.1 1.5 2.5 2.8 2.8 3.1 2.8 1.5 2.1 3.2 1.3 1.3 1.1 1.2 1.7 1.1 1.1 1.0 1.8 1.1 1.6 1.8

β 0.0 0.2 0.3 0.4 0.5 0.5 0.7 0.9 0.3 0.3 0.4 0.4 0.5 0.5 0.5 0.4 0.2 0.3 0.8 0.4 0.4 0.4 0.3 0.3 0.3 0.3 0.3 0.4 0.4 0.5 0.5

γ 0.0 0.1 0.1 0.1 0.2 0.2 0.2 0.1 0.1 0.1 0.1 0.2 0.3 0.1 0.2 0.0 0.1 0.1 0.1 0.1 0.1 0.1 0.0 0.1 0.1 0.1 0.1 0.1 0.2 0.3 0.3

Starting value and equations for CH3's H 3C

δ CH3 = 0.9 + ∑(β + γ)

H3C Cβ Cγ

∑ is the summation symbol for all substituents considered Starting value and equation for CH2's In a similar manner we can calculate chemical shifts for methylenes (CH2) using the following formula δ CH2 = 1.2 + ∑(α +β + γ)

H 3C

∑ is the summation symbol for all substituents considered Starting value and equation for CH's In a similar manner we can calculate chemical shifts for methines (CH) using the following formula δ CH = 1.5 + ∑(α +β + γ)

∑ is the summation symbol for all substituents considered

H c. methyl

e. methylene f. methylene a. methyl = 0.9 + (1.5)α + (0.1)γ = 2.5 ppm actual = 2.6

d. methyl = 0.9 + (0.1)α = 1.0 ppm actual = 1.0

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

e. methylene = 1.2 + (0.3)α = 1.5 ppm actual = 1.7

c. methine = 1.5 + (1.4)α + (2.3)α + (0.2)β = 5.4 ppm actual = 5.2

f. methylene = 1.2. + (1.7)α = 2.9 ppm actual = 2.9

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H C α Cβ C γ

CH3 CH2 HO N CH O

H 2C H 2C

H H C α Cβ C γ

a. methine b. methylene

d. methyl

α

δ CH3 = 0.9 + α

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Estimated chemical shifts for protons at alkene sp2 carbons Substituent HHydrogen RAlkyl C6H5CH2Benzyl X-CH2Halomethyl (H)/ROCH2alkoxymethyl (H)2/R2NCH2aminomethyl RCOCH2α-keto NCCH 2α-cyano R2C=CRAlkenyl C6H5...