Acylation Alkylation

Reagents treated in this section have proved to be especially suitable for handling the various nitrogen protic groups for which silylation with TMS donors is clearly inferior due to the lability of the N-Si bond. A comprehensive review on the derivatization of amines for GC analysis has been published by Kataoka (see Further Reading).

The perfluorinated anhydrides, despite their much higher molecular weight, yield derivatives of high volatility since interaction between the perfluoroal-kane chain and a nonfluorinated stationary phase is substantially weakened. The retention of perfluoroal-kyl(acyl) derivatives is, therefore, often markedly less

Table 1 Electrophoric reagents frequently used for esterification, acylation and alkylation

Haloalkyl(acyl) group

Matrix

Formula

b.p. (OC)

Abbreviation

2-Chloro-

Ethanol

CICH2CH2OH

129

2CE

2,2,2-TrichIoro-

Ethanol

CCI3CH2OH

151

TCE

Ethyl chloroformate

CCI3CH2OCOCI

171

TCECF

2,2,2-TrifIuoro-

Ethanol

CF3CH2OH

78

TFE

Acetic anhydride

(CF3CO)2O

40

TFAA

Chlorodifluoro-

Acetic anhydride

(CF2CICO)2O

96

CDFAA

1,1,1,3,3,3-HexafIuoro-

Isopropanol

(CF3)2CHOH

59

HFIP

2,2,3,3,3-PentafIuoro-

Propanol

c2f5ch2oh

81

PFP

Propionic anhydride

(C2F5CO)2O

96

PFPA

2,2,3,3,4,4,4-HeptafIuoro-

Butanol

c3f7ch2oh

96

HFB

Butyric anhydride

(C3F7CO)2O

108

HFBA

Butyryl chloride

C3F7COCI

39

HFB-CI

Pentafluorobenzoyl

Chloride

C6F5CH2COCI

158

PFB-CI

Pentafluorobenzyl

Bromide

C6F5CH2Br

174

PFBBr

Chloroformate

C6F5CH2OCOCI

PFBCF

Hydroxylamine

C6F5CH2ONH2

PFBHA

Aldehyde

C6F5CHO

165

PFBA

than that of their hydrocarbon analogues. Another reason for their popularity is the high sensitivity to ECD, which increases rapidly with increase in F substitution. The response can be further augmented by incorporation of Cl, Br or I atoms into the molecule but the volatility of such derivatives declines rapidly and reagents carrying more than three Cl atoms are unsuitable for derivatization of higher mass analytes.

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