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Factoring Isotope Patterns Chlorine and Bromine
withnitrogen
Ray A. Gross, Jr.Prince George’s Community College
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Outline
• Develop an equation for the isotope patterns of BrmCln compounds
• Show the isotope-patterns equal two independent factors: Br and Cl factors
• Show that the chlorine factor and n are evident by the first term in the isotope pattern.
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156
Br m = 1T = 2
1:1
100 61 59
100 98
Brm
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Cl
Cln
n = 1T = 2
52 100 31
100 32
3:1
112
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Br
Cl
BrmCln
m = 1 n = 1 T = 3
77 100 24
78 100 24
3:4:1
190
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Bromine Binomial
• Ratio of Br-79 to Br-81 = 1:1
• (a + b)m for Brm
• (a + b)1 = a + b = 1:1
• (a + b)2 = a2 + 2ab + b2 = 1:2:1
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Chlorine Binomial
• Ratio of Cl-35 to Cl-37 = 3:1
• (3a + b)n for Cln
• (3a + b)1 = 3a + b = 3:1
• (3a + b)2 = 9a2 + 6ab + b2 = 9:6:1
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Ideal Model
(1a + 1b)m(3a + 1b)n
Br1Cl1
3a2 + 4ab + 1b2 = 3:4:1
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Isotope Pattern (I.P.) equals a product of Br and Cl factors
I.P. = (1a + 1b)m(3a + 1b)n
3:4:1 = (1:1)1(3:1)1
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Premise
• Because an isotope pattern for a BrmCln
compound is composed of the product of a bromine factor and a chlorine factor, the pattern should be divisible by either factor to give the other factor.
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Question
• For 27: 81: 90: 46: 11: 1
• What factor do we divide by?
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Bromine and Chlorine Factors
m or n Bromine
(1:1)m
Chlorine
(3:1)n
Terms
T
1 1:1 3:1 2
2 1:2:1 9:6:1 3
3 1:3:3:1 27:27:9:1 4
4 1:4:6:4:1 81:108:54:12:1 5
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Results
• The lead term in a normalized pattern equals 3n.
• The value of n determines the chlorine factor.
• T = m + n + 1, or m = T – (n + 1)
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9:15:7:1 = (9:6:1) (1:1)m
1: 1 9: 6 : 19: 6 :1) 9: 15: 7: 1 1:1) 9: 15: 7 : 1 9: 6: 1 9 : 9 9: 6: 1 6 : 7 9: 6: 1 6 : 6 1 : 1 1 : 1
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T = m + n + 1
_ _ _ 1: 2: 1
27: 81: 90: 46: 11: 1
27: 27: 9: 1 _ _
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Br2Cl3
27 Cl Cl Cl Br Br
27: 81: 90: 46: 11: 1
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224
10:17:7:1
62 100 45 6Unknown
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224
10:17:7:1
62 100 45 6
UnknownBr
10:17: 7 : 1 9:Cl:Cl:Br
224149 = Br1Cl2 75 = benzene residue
Cl
Cl
Mass spectrum of 1-bromo-2,4-dichlorobenzene
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M = 283
85 190 132 26
3:7: 5:1
Unknown
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NH2
M = 283 = N1
Figure 4. Mass spectrum of 2,6-dibromo-4-chloroaniline.
BrBr
Cl
283207 = Br2Cl1N1 76 = benzene residue
85 190 132 26
3:7: 5:13 : 7 : 5 : 13 Cl Br BrUnknown
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Summary
• The lead number in a normalized isotope pattern of an unknown BrmCln
compound uniquely defines n and the corresponding chlorine factor within the pattern.
• Given n, the number of bromine atoms can be found from the number of terms T in the pattern.
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Acknowledgements
• Junhua Yan’s Isotope Pattern Calculator http://www.geocities.com/junhuayan/pattern.htm (accessed May 2003).
• Institute of Advanced Industrial Science and Technology; Tsukuba, Ibaraki, Japan
SDBSWeb: http://www.aist.go.jp/RIODB/SDBS/ (accessed May 2003).
• NSF Grant: DUE-0202431
• Submitted to The Chemical Educator