20 th biennial conference on chemical education indiana university, bloomington, indiana, july 27,...
TRANSCRIPT
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