20th Biennial Conference onChemical Education

Indiana University, Bloomington, Indiana, July

27, 2008

Solving Qualitative Organic Problems with the Aid of an Automated Isotope-Pattern

Analyzer

Ray A. Gross, Jr.Prince George’s Community

College

Introduction

• Many aryl compounds contain small combinations of Br, Cl and S atoms.

• The Br, Cl, S stoichiometry of most of these compounds is revealed in their characteristic molecular-ion peaks in their low-resolution mass spectra

• An automated isotope-pattern analyzer has been developed that determines the A + 2 composition of these compounds.

Outline

• Three qual-organic problems will be solved with the aid of the IPA.

• The IPA will be demonstrated.

Problem 1

•

What is the Br, Cl, S composition?

Spectrum: Spectral Database for Organic Compounds, SDBS

Problem 1

•

What is the Br, Cl, S composition?

M = 288 (11.5%)M + 2 = 290 (8.5%)M + 4 = 292 (2.0%)

Spectrum: Spectral Database for Organic Compounds, SDBS

3,4-toluenedisulfonyl dichloride

SO2Cl

SO2Cl

Cl2S2

Problem 2Compound A: mp 82 oC

m/e %

194 49.4

195 10.4

196 47.0

197 5.8

198 16.1

199 1.2

200 1.6

201 0.1

Compound A: Cl3

75

3 Cl

105

194 - 180 = 14 = Me

= 180

Cl

Cl

Cl

Cl

Cl

Cl

mp ~ 82 oC

194

Compound A: 2,4,6-trichlorotoluene

Problem 3

Compound A (mp 38 oC)

Compound Bhydrolysis

m/e %244 26.0246 26.2248 9.1250 1.3

m/e %226 100.0228 64.9230 12.5

Compound A: Cl3S1

Compound B: Cl2S1

Compound A: 2,4-dichlorobenzenesulfonyl chloride

Compound A (mp 38 oC)

Compound Bhydrolysis

m/e %244 26.0

m/e %226 100.0

Cl3S1 Cl2S1

244 - 35 = 209; 209 + 17 = 226

Cl

75 35

Cl Cl S

35 35 32 = 212

244 - 212 = 32 = 2 oxygen atoms

Cl Cl

SO2Cl

mass = 244

SO2Cl

ClCl

mp ~ 38 oC

Conclusion

• The IPA is a useful tool for qualitative organic analysis.

• Finds A + 2 compositions for 21 combinations of Br, Cl and S.

J. Chem Educ., 2007 84, 987-991