1

Analysis of the Isotope Patterns of Organic Sulfur Containing Compounds

Ray A. Gross, Jr.

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Outline

• Theoretical Isotope Patterns• Real Isotope Patterns• New Method of Determining # S Atoms

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A/(A + 2) Isotope Ratios

r 30:1 30 (3)28 (92)Silicon

p 500:1 18 (0.2)16 (99.8)Oxygen

q 22:1 34 (4.29)32 (94.93)Sulfur

n 3:1 37 (24)35 (76) Chlorine

m 1:1 81 (49)79 (51) Bromine

Variable# atoms

Ratioa/b

ba Element

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Bromine Binomial Model for A + 2 Molecular Ion Intensities

• Ratio of 79Br to 81Br = 1:1

• (a + b)m for Brm

• (a + b)1 = 1a + 1b = 1:1

• (a + b)2 = 1a2 + 2ab + 1b2 = 1:2:1

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Chlorine Binomial Model for A + 2 Molecular Ion Intensities

• Ratio of 35Cl to 37Cl = 3:1

• (3a + b)n for Cln

• (3a + b)1 = 3a + b = 3:1

• (3a + b)2 = 9a2 + 6ab + 1b2 = 9:6:1

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Sulfur A + 2 Binomial

• Ratio of 32S to 34S = 22:1

• (22a + b)q for Sq

• (22a + b)1 = 22a + 1b = 22:1

• (22a + b)2 = 484a2 + 44ab + 1b2 = 484:44:1

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SqSulfur Isotope Patterns

Normalized to Highest Mass = 1(22:1)q

RatioM/M + 2

S122 : 1 22

S2484 : 44 : 1 11

S310648 : 1452 : 66 : 1 7.3

S4234256 : 42592 : 2904 : 88 : 1 5.5

S55153632 : 1171280 : 106480 : 4840 : 110 : 1 4.4

S6113379904 : 30921792 : 3513840 : 212960 :

7260 :132 :13.7

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SqSulfur Isotope PatternsNormalized to M = 100

(22:1)q

Ratio M/M + 2

(T)S1

100 : 4.5 22 (2)

S2100 : 9 : 0.2 11 (2)

S3100 : 14 : 0.6 : 0.01 7.3 (2)

S4100 : 18 : 1.2 : 0.03 : 0.0004 5.5 (2/3)

S5100 : 23 : 2.1 : 0.09 : 0.002 : 0.00002 4.4 (2/3)

S6100 : 27: 3 : 0.2 : 0.006 : 0.0001 : 0.0000008 3.7 (2/3)

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SqRatio

M/M + 2(T)

Yan RatioM/M +2

(T)S1 22 (2) 22.2 (2)

S2 11 (2) 11.1 (2)

S3 7.3 (2) 7.35 (2)

S4 5.5 (2/3) 5.52 (3)

S5 4.4 (2/3) 4.41 (3)

S6 3.7 (2/3) 3.68 (3)

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S

M = 134 100.0M + 1 = 135 9.8M + 2 = 136 4.8

M/(M + 2) = 100.0/4.8 = 21 = S1

M = 134 136

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223.0 100.0 224.0 12.4 225.0 6.0

M = 223

R2 = 17

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M +1 +2 +3 M +1 +2 +3

100 9.0 (11)100.0 4.5 (22)

S1 S2

C20H42N4O4S1

100.0 8.2 (12) 100 12.9 (7.75)

C20H42N4O4S2

Rel

ativ

e In

tens

ity

Rel

ativ

e In

tens

ity

m/z m/z

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223 100.0224 12.4225 6.0R2 = 17

S1 = 12-22S2 = 7.75-11

NH2 SO3H

S1

M = 223

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Intensity Ratios for Real Compounds Containing Sulfur

Number S AtomsSample Size

R2 R4 R24

1 >100 12-23

2 >100 7.7-12

3 47 5.59-7.4

4 12 4.66-5.53 50-71 11-14

5 10 3.68-4.70 31-51 8.5-10.8

6 2 3.69-3.12 21.5-31.5 7.09-8.71

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CH3(CH2)3SS(CH2)3CH3

178 180

M = 178.0 33.6 M + 2 = 180.0 3.1

33.6/3.1 = 11 = S2

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Intensity Ratios for Real Compounds Containing Sulfur

Number S Atoms R2 R4 R24

1 12-23

2 7.7-12

3 5.59-7.4

4 4.66-5.53 50-71 11-14

5 3.68-4.70 31-51 8.5-10.8

6 3.69-3.12 21.5-31.5 7.09-8.71

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SS

S

M = 136.0 100.0 M + 2 = 138.0 13.6

100.0/13.6 = 7 = S3

136 138

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Intensity Ratios for Real Compounds Containing Sulfur

Number S Atoms R2 R4 R24

1 12-23

2 7.7-12

3 5.59-7.4

4 4.66-5.53 50-71 11-14

5 3.68-4.70 31-51 8.5-10.8

6 3.69-3.12 21.5-31.5 7.09-8.71

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S S CN(Et)2

S

(Et)2NC

S

M = 296.0 17.9 M + 2 = 298.0 3.4

17.9/3.4 = 5 = S4

296 298

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Intensity Ratios for Real Compounds Containing Sulfur

Number S Atoms R2 R4 R24

1 12-23

2 7.7-12

3 5.59-7.4

4 4.66-5.53 50-71 11-14

5 3.68-4.70 31-51 8.5-10.8

6 3.69-3.12 21.5-31.5 7.09-8.71

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332 100.0334 18.9336 1.4

R2 = 5.29; R4 = 71; R24 = 14

S4: R2 = 4.66-5.53 R4 = 50-71 R24 = 11-14

S

NN

SS S

S4

M = 332

22

M = 406

406 4.3408 1.1

R2 = 3.9

S5: R2 = 3.68-4.70

S S

S SC CO O

S

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S

S S

SS

S5

224 100.0226 22.2228 2.3

R2 = 4.50, R4 = 44, R24 = 9.7

M = 224

S5: R2 = 3.68-4.70 R4 = 31-51 R24 = 8.5-10.8

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Conclusion

• The intensity-ratio method is an efficient tool for determining small numbers of sulfur atoms in an unknown from its mass spectrum.

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Acknowledgments

• SDBS– http://www.aist.go.jp/RIODB/SDBS/cgi-bin/

cre_index.cgi• NIST

– http://physics.nist.gov/PhysRefData/Compositions/index.html

• Yan– http://www.geocities.com/junhuayan/pattern.htm