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Beauchamp Spectroscopy Tables 1, Study notes of Chemistry

Infrared Tables (short summary of common absorption frequencies). The values given in the tables that follow are ... carboxylic acid C=O (also acid "OH").

Typology: Study notes

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Beauchamp Spectroscopy Tables 1
Z:\classes\spectroscopy\all spectra tables for web.DOC
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)
CC
not used
CN
1000-1350
CC CC
CO
1050-1150
CC CN CO
1250 1100-1350
1600-1680
sp
3
C-X single bonds sp
2
C-X single bonds
sp
2
C-X double bonds sp C-X triple bonds
CN
1640-1690
CO
1640-1810
CN
2100-2250 2240-2260
Stronger dipoles produce more intense IR bands and weaker dipoles produce less intense IR bands (sometimes none).
expanded table
on next page
acyl and phenyl C-Oalkoxy C-O not very useful
not very useful
Bonds to Hydrogen (stretching wave numbers)
CH
2850-3000
3000-3100
CCH
CH
O
CN
H
H
3300
sp
3
C-H
sp
3
C-H sp
3
C-H aldehyde C-H
(two bands)
primary NH
2
(two bands) alcohol O-H
secondary N-H
(one band) acid O-H thiol S-H
CH
2700-2760
2800-2860
3100-3500
CN
H
3100-3500 3200-3400
OHR
2500-3400
OHC
O
2550 -2620
(very weak)
SHR
amides = strong, amines = weak
(see sp
2
C-H bend
patterns below) (sp C-H bend 620)
pf3
pf4
pf5
pf8
pf9
pfa
pfd
pfe
pff

Partial preview of the text

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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

. 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 1 H and 13 C 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

-

Bonds to Carbon (stretching wave numbers)

C C

not used

C N

1000-

C C C^ C

C O

1050-

C C (^) C N

C O

1250

1100-

1600-

sp^3 C-X single bonds (^) sp 2 C-X single bonds

sp^2 C-X double bonds sp C-X triple bonds

C N

1640-

C O

1640-

C N

2100-2250 2240-

Stronger dipoles produce more intense IR bands and weaker dipoles produce less intense IR bands (sometimes none).

expanded table on next page

not very useful alkoxy C-O not very useful acyl and phenyl C-O

Bonds to Hydrogen (stretching wave numbers)

C H

C C H C H

O

C N

H

H

sp^3 C-H

sp^3 C-H sp^3 C-H aldehyde C-H (two bands)

primary NH 2 (two bands) (^) alcohol O-H

secondary N-H (one band) acid O-H (^) thiol S-H

C H

C N

H 3100- 3200-

R O H

C O H

O

(very weak)

R S H

amides = strong, amines = weak

(see sp^2 C-H bend patterns below) (sp C-H bend^ ≈^ 620)

Carbonyl Highlights (stretching wave numbers)

C

O

R H

Aldehydes (^) Ketones Acids

Amides Anhydrides^ Acid Chlorides

saturated = 1725 conjugated = 1690 aromatic = 1700

C

O

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

C

O

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

Esters

C

O

R O saturated = 1715 conjugated = 1690 aromatic = 1690

C

O

R NR (^2) saturated = 1650 conjugated = 1660 aromatic = 1660 6 atom ring = 1670 5 atom ring = 1700 4 atom ring = 1745 3 atom ring = 1850

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

C

O

R Cl saturated = 1800 conjugated = 1770 aromatic = 1770

C

O

R O

O

R

R' H

R N

O

O

nitro

asymmetric = 1500- symmetric = 1300-

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.,

sp^2 C-H bend patterns for alkenes sp^2 C-H bend patterns for aromatics

alkene substitution pattern

aromatic substitution pattern

descriptive alkene term

descriptive aromatic term

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

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

C C

R

H

H

H

C C

R

H

R

H

monosubstituted alkene

cis disubstituted alkene

trans disubstituted alkene

geminal disubstituted alkene

trisubstituted alkene

tetrasubstituted alkene

985- 900-

675- (broad)

880-

960-

790-

none

X

X

X

X

X

X

X

monosubstituted aromatic

ortho disubstituted aromatic

meta disubstituted aromatic

para disubstituted aromatic

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.

C C

R

H

H

R

C C

R

R

H

H

C C

R

R

R

H

C C

R

R

R

R

690- 730-

735-

680- 750- 880-900 (sometimes)

790-

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

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

does not have C=O band

IR Spectrum

aldehydes

C

O

aldehyde C-H

1725-1740 (saturated) 1660-1700 (unsaturated) 2860- 2760- (both weak)

ketones

C

O (^) 1710-1720 (saturated) 1680-1700 (unsaturated) 1715-1810 (rings: higher in small rings) esters - rule of 3

C

O

(1000-1150, alkoxy, medium)

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

C O acids

C

O

1210-1320 (acyl, strong)

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

C O

O H

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

C

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

N

H

H

N H

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

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

acid chlorides

C

O 1800 (saturated) 1770 (unsaturated)

anhydrides

C

O

1150-1350 (acyl, strong)

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

C O

nitriles ≈^2250 sharp, stronger than alkynes, a little lower when conjugated

alkanes

C C C N

alkynes

alkenes

aromatics

alcohols

thiols

amines

ethers

nitro compounds

N O

O

carbon-halogen bonds

sp^3 C-H stretch sp 3 C-H bend C C not useful

1460 & 1380

2850-

C X (^) usually not very useful

sp^2 C-H stretch

sp^2 C-H bend

C C (^) weak or not present1600-

650- (see table for spectral patterns)

3000-

sp^2 C-H stretch 3050-

sp^2 C-H bend

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

C C 1600 & 1480 can be weak

O H

alcohol

C O

3600- 1000- (3o^ > 2o^ > 1 o^ )

S H

thiol ≈^ 2550 (weak)

N

H

H

N H

3300 - 3500, two bands for 1o^ amines, one band for 2o^ amines, weaker than in amides, N-H bend, 1550-1640, stronger in amides than amines N H

N C 1000- (uncertain)

1120 (alphatic) C O 1040 & 1250 (aromatic)

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

C N

C C

sp C-H stretch

sp C-H bend

2150 (variable intensity)

3300 sharp, strong 620

not present or weak when symmetrically substituted, a little lower when conjugated

sometimes lost in sp^3 CH peaks

C O

acyl alkoxy

1150-1350 (acyl, strong)

acyl

1 o 2 o

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

acyl

All IR values are approximate and have a range of possibilities depending on the molecular environment in which the functional group resides. Resonance often modifies a peak's position because of electron delocalization (C=O lower, acyl C-O higher, etc.). IR peaks are not 100% reliable. Peaks tend to be stronger (more intense) when there is a large dipole associated with a vibration in the functional group and weaker in less polar bonds (to the point of disappearing in some completely symmetrical bonds).

1 o 2 o

alkoxy

(easy to overlook)

alkoxy

X = F, Cl, Br, I

Alkene sp 2 C-H bending patterns

monosubstituted alkene (985-1000, 900-920) geminal disubstituted (960-990) cis disubstituted (675-730) trans disubstituted (880-900) trisubstituted (790-840) tetrasubstituted (none, no sp^2 C-H)

Aromatic sp^2 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)

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.

(^1211109876543210)

(^240220200180160140120100806040200)

typical proton chemical shifts

typical carbon-13 chemical shifts

simple sp 3 C-H CH > CH 2 > CH 3

C C C

O C

OC

H

X C X = F,Cl,Br,I

C H

alcohol O H

allylic C-H

benzylic C-H carbonyl alpha C-H

amine N-H

epoxide C-H

alkene C-H

aldehyde C-H aromatic C-H

carboxylic acid O-H

amide N-H

alcohols ethers esters

shielding side = more electron rich (inductive & resonance)

deshielding side = less electron rich (inductive & resonance)

alcohols, ethers, esters

C C N C

carboxylic acids anhydrides esters amides acid chlorides

R

C

O

X

R

C

O

R ketones

R

C

O

H aldehydes

halogen C

PPM

PPM

F ≈ 80- Cl ≈ 45- Br ≈ 35- I ≈ 15-

210 180

180 160

220 +^180

125 110

90 + 70 -

160 +^100 - 60 +^0

80 + 50

95 15

10 9 8 + 6 5 + 3.3 3 2 2 0.

12 10

7 +^4

3.5 2.

3 + 2

5 3 2.5 1.

(^6 )

1

2 1

5

simple sp^3 carbon C > CH > CH 2 > CH 3

no H

with H

no H

with & without H

no H

with & without H

with & without H

with & without H

with & without 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.

O

epoxides with & without H 60 40 S C

with & without H

thiols, sulfides

40 20

thiol SH 1.5 1.

thiols, sulfides 2.5 2.

50 30

N C

with & without H

amines, amides

amines

H 3.0 2.

S C H

N C H

Typical 1 H and 13 C NMR chemical shift values.

CH 3 O

C

C

H

H

H

Example Calculation

δb = 5.2 + (-0.6) = 4. actual = 4.6 (J = 6, 1.6 Hz)

C C

H

gem

cis

trans δ(ppm) = 5.2 + α (^) gem + α (^) cis + α (^) trans

Substitution relative to calculated "H"

gem

trans

cis

δ gem = 5.2 + 1.4 = 6. actual = 6.

δ trans = 5.2 - 0.1 = 5. actual = 5.

δ cis = 5.2 + 0.4 = 5. actual = 5.

Estimated chemical shifts for protons at alkene sp 2 carbons

Substituent α (^) geminal α (^) cis α (^) trans

H- 0.0 0.0 0. Hydrogen R- 0.5 -0.2 -0. Alkyl C 6 H 5 CH 2 - 0.7 -0.2 -0. Benzyl X-CH 2 - 0.7 0.1 0. Halomethyl (H)/ROCH 2 - 0.6 0.0 0. alkoxymethyl (H) 2 /R 2 NCH 2 - 0.6 -0.1 -0. aminomethyl RCOCH 2 - 0.7 -0.1 -0.

α-keto NCCH 2 - 0.7 -0.1 -0.

α-cyano R 2 C=CR- 1.2 0.0 0. Alkenyl C 6 H 5 - 1.4 0.4 -0. Phenyl F- 1.5 -0.4 -1. Fluoro Cl- 1.1 0.2 0. Chloro Br- 1.1 0.4 0. Bromo I- 1.1 0.8 0. Iodo RO- 1.2 -1.1 -1. akoxy (ether) RCO 2 - 2.1 -0.4 -0. O-ester (H) 2 /R 2 N- 0.8 -1.3 -1. N-amino RCONH- 2.1 -0.6 -0. N-amide O 2 N- 1.9 1.3 0. Nitro RS- 1.1 -0.3 -0. Thiol OHC- 1.0 1.0 1. Aldehyde ROC- 1.1 0.9 0. Ketone HO 2 C- 0.8 1.0. 03 C-acid RO 2 C- 0.8 1.0 0. C-ester H 2 NOC- 0.4 1.0 0. C-amide NC- 0.3 0.8 0. Nitrile

C C

H

H

H

O C

O

C C

H H

a H

b

c (^) d e

f

δa = 5.2 + (-0.4) = 4. actual = 4.9 (J = 14, 1.6 Hz)

δc = 5.2 + 2.1 = 7. actual = 7.4 (J = 14, 6 Hz) δd = 5.2 + 0.8 = 6. actual = 6.2 (J = 18, 11 Hz) δe = 5.2 + 0.5 = 5. actual = 5.8 (J = 11, 1.4 Hz) δf = 5.2 + 1.0 = 6. actual = 6.4 (J = 18, 1.4 Hz)

Estimated chemical shifts for protons at aromatic sp 2 carbons

Substituent α ortho α meta α para

H- 0.0 0.0 0. Hydrogen CH 3 -^ -0.2^ -0.1^ -0. Methyl ClCH 2 - 0.0 0.0 0. Cholromethyl Cl 3 C- 0.6 0.1 0. Halomethyl HOCH 2 - -0.1 -0.1 -0. Hydroxymethyl R 2 C=CR- 0.1 0.0 -0. Alkenyl C 6 H 5 - 1.4 0.4 -0. Phenyl F- -0.3 0.0 -0. Fluoro Cl- 0.0 0.0 -0. Chloro Br- 0.2 -0.1 0. Bromo I- 0.4 -0.2 0. Iodo HO- -0.6 -0.1 -0. Hydroxy RO- -0.5 -0.1 -0. Alkoxy RCO 2 - -0.3 0.0 -0. O-ester (H) 2 /R 2 N- -0.8 -0.2 -0. N-amino RCONH- 0.1 -0.1 -0. N-amide O 2 N- 1.0 0.3 0. Nitro RS- -0.1 -0.1 -0. thiol/sulfide OHC- 0.6 0.2 0. Aldehyde ROC- 0.6 0.1 0. Ketone HO 2 C- 0.9 0.2 0. C-acid RO 2 C- 0.7 0.1 0. C-ester H 2 NOC- 0.6 0.1 0. C-amide NC- 0.4 0.2 0. Nitrile

δ(ppm) = 7.3 + α (^) ortho + α (^) meta + α (^) para

Substitution relative to calculated "H"

H

meta ortho

para

meta (^) ortho

Example Calculation

CH 3 O

H

H

H

H CH 2

H

H

H

  1. δ (CH 3 ) = 0.9 + 2.8 = 3. actual = 3.
  2. δ (2) = 7.3 + (-0.5) (^) ortho + (-0.1) (^) para = 6. actual = 6.
  3. δ (3) = 7.3 + (-0.2) (^) ortho + (-0.4) (^) para = 6. actual = 7.
  4. δ (CH 2 ) = 1.2 + (0.8)α + (1.4)α = 3. actual = 3.
  5. δ (5) = 5.2 + (0.7) (^) gem = 5. actual = 5.
  6. δ (6) = 5.2 + (-0.2) (^) trans = 5. actual = 5.
  7. δ (7) = 5.2 + (-0.2) (^) cis = 5. actual = 5.

Proton chemical shifts of hydrogen on sp^3 carbons depend on two main factors (electronegativity and pi

bond 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 (CH 2 ) which have greater chemical shifts than methyl protons (CH 3 ).

C H (^) C H

H C H

H

H

Chemical shifts in an only "alkane" environment.

δ 1.5 ppm δ 1.2 ppm^ δ 0.9 ppm methine protons methylene protons^ methyl protons

1. sp

3

C-H Electronegative atoms 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.

(r esonance withdrawal)

C F

H C Cl

H C Br

H C I

H

C N

H

δ 2.3 - 3.1 ppm

δ 4.1 - 4.7 ppm

C OH

H C OR

H C O

H (^) C

O R C O

H C O

H (^) C

O

δ 3.1 - 3.7 ppm (^) δ 3.0 - 3.6 ppm δ 2.9 - 3.5 ppm

amines amides

fluoro alkanes (^) chloro alkanes (^) bromo alkanes iodo alkanes

δ 3.1 - 3.7 ppm alcohol alkyl ether (^) aromatic ether alkyl ester (oxygen side)

aromatic ester (oxygen side)

δ 3.0 - 3.6 ppm^ δ 3.7 - 4.3 ppm^ δ^ 3.7 - 4.3 ppm^ δ^ 4.0 - 4.6 ppm

C SH

H C SR

H

δ 2.2 - 2.8 ppm thiol alkyl ether

δ 2.2 - 2.8 ppm

(resonance withdrawal) (resonance withdrawal) (resonance withdrawal)

C

O

H δ 2.5 - 3.2 ppm epoxide ether

a. next to a halogen

b. next to a oxygen

c. next to a sulfur or nitrogen

δ 3.0 - 3.6 ppm

C N

H (^) C

O

2. sp

3

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 sp

3

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.

C C

H (^) O

aldehydes, ketones, carboxylic acids, amides, alkyl ester (oxygen side)

aromatic ketones

δ 1.9 - 2.7 ppm δ 2.6 - 3.3 ppm

C C

H (^) O

(resonance withdrawal)

acid chlorides

δ 2.7 - 3.4 ppm (resonance withdrawal)

C C

H (^) O

Cl

nitro compounds

δ 2.7 - 3.4 ppm (resonance withdrawal)

C N

H (^) O

O

C C

H (^) C

allylic protons

δ 1.7 - 2.3 ppm

C

H

benzylic protons

δ 2.3 - 2.9 ppm propargylic protons

δ 1.8 - 2.4 ppm

C

H C C

3. sp^2 C-H Hydrogens 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)

vinylic protons (resonance and inductive withdrawal)

R C

C

H

H H

simple vinylic protons

δ 5.7 ppm

δ 5.0 ppm

C C

C

H

H O H

δ 6.0 - 6.3 ppm

δ 5.5 - 6.5 ppm

RO C

C

H

H H

δ 6.4 - 7.4 ppm

δ 4.0 - 4.6 ppm

vinylic protons (resonance donation and inductive withdrawal)

aromatic protons (resonance and inductive withdrawal)

simple aromatic protons

δ 7.1 - 7.3 ppm

aromatic protons (resonance donation and inductive withdrawal)

H

R

H

C

O

δ 7.9 - 8.3 ppm

H

O

δ 6.7 - 7.0 ppm H

N

δ 6.5 - 7.0 ppm

aldehydes

δ 9 - 10 ppm

C

O

H

alkene C-H

aromatic C-H

aldehyde C-H (^) alkyne C-H

C C H

terminal alkyne protons

δ 1.9 - 3.2 ppm

C C

C

H

H O H RO C

C

H

H H

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/base 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.

alcohols

δ 1 - 5 ppm

O

H

phenol and enol protons

δ 7 - 15 ppm

O

H

O

H

amines

δ 1 - 2 ppm

N

H

carboxylic acids

δ 10 - 12 ppm

C

O

O H

C

O

N H

amides

δ 1 - 6 ppm

  1. One nearest neighbor proton

∆E (^) to flip proton

increasing δ increasing ∆E (ν, B (^) o )

the ratio of these two populations is about 50/50 (or 1:1)

∆E 1 (observed)

∆E 2 (observed)

observed proton

one neighbor proton = Ha

B (^) o

Protons in this environment have a small additional increment added to the external magnetic field, Bo , and produce a higher energy transition by that tiny amount.

Protons in this environment have a small cancellation of the external magnetic field, B (^) o , and produce a smaller energy transition by that tiny amount.

small difference in energy due to differing neighbor's spin (in Hz)

J = coupling constant

C C

H (^1) H (^) a

H (^1)

C C C C

H (^1)

H (^1)

(^1 )

  1. Two nearest neighbor protons (both on same carbon or one each on separate carbons)

∆E (^) to flip proton

the ratio of these four populations is about 1:2:

∆E (^1)

observed proton

two neighbor protons

B (^) o

J (Hz)

C C

H (^) a H (^) b

H (^1)

H (^1)

C C

H (^1)

1 2

∆E (^2) ∆E 3 J1a

1

J1b J1b two equal energy two neighbor protons are liketwo small magnets that can be populations here

arranged four possible ways (similar to flipping a coin twice) J (Hz)

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

∆E (^) to flip proton

the ratio of these eight populations is about 1:3:3: observed proton

three neighbor protons

B (^) o

C C

H (^) a H (^) b H (^) c

H (^1)

H (^1)

C C

H (^1)

3

∆E (^2) ∆E 3 J1a

1

J1b J1b

three equal energy populations at each of middle transitions

three neighbor protons are like three small magnets that can be arranged eight possible ways (similar to flipping a coin thrice)

∆E (^1)

∆E (^4)

3 1

J1c J1c J1c

δ (ppm)

δ (ppm)

δ (ppm)

N + 1 rule (N = # neighbors)

peaks = N + 1 = 1 + 1 = 2 peaks

N + 1 rule (N = # neighbors)

peaks = N + 1 = 2 + 1 = 3 peaks

N + 1 rule (N = # neighbors)

peaks = N + 1 = 3 + 1 = 4 peaks

perturbation(s) by neighbor proton(s)

J (Hz)

J (Hz) J (Hz) J (Hz)

J1a

s = singlet

d = doublet

t = triplet

q = quartet

qnt = quintet

sex = sextet

sep = septet

o = octet

1 peak = 100%

1 peak = 50%

1 peak = 25%

1 peak = 12%

1 peak = 6%

1 peak = 3%

1 peak = 1.5%

1 peak = 0.8%

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

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.

relative sizes of

peaks in multiplets