Mass spectra of chlorinated esters: 2—Methyl mono- and dichlorobutanoates

The mass spectral fragmentations of methyl mono- and dichlorobutanates have been studied. Deutrium labelling and metastable ion analysis were used to elucidate the fragmentation mechanisms. The molecular ion peaks of the esters are weak and show only in the spectra of the monochloro isomers. A McLafferty rearrangement gives the base peaks in the spectra of methyl 2-chloro-, 4-chloro- and 4,4-dichlorobutanoate; α-cleavage, [COOCH3]+, in methyl 2,2- and 2,4-dichlorobutanoate; [MCl]+, in methyl 3-chlorobutanoate; [MClHCl]+, in methyl 3,4-dichlorobutanoate; [MClCH2CO]+, in methyl 3,3-dichlorobutanoate and [MClCOOCH3]+˙, in methyl erythro- and threo-2,3-dichlorobutanoate. The mass spectra of the…

Mass spectra of halogenated esters. 7. Methyl esters of 2-chloro C2C20n-alkanoic acids

The mass spectral fragmentation of a homologous series of methyl esters of 2-chloro n-alkanoic acids ranging from acetic (C2) to eicosanoic (C20) acid on electron impact has been investigated. The fragmentation pathways were elucidated with the aid of the first field-free region metastable ions, the results being presented with one compound, i.e. with ionized methyl 2-chloro-octauoate. Owing to the Cl/H exchanges and to the formation of the non-chlorinated parent esters prior to the fragmentations the spectra show the peak pairs with and without the chlorine atom. The effects become more evident with increasing chain length; shown most visually by the abundance ratios of the McLafferty rear…

Gas-liquid chromatography and lipophilicity of esters of benzoic acids

Abstract The use of gas-liquid chromatographic (GLC) retention indices for the determination of lipophilicity was studied for a series of alkyl and arylalkyl esters of substituted benzoic acids. The regression relationships between the logarithms of the partition coefficients and the retention characteristics measured on two cpillary columns, SE-30 and OV-351, were evaluated. The behaviour of arylalkyl esters and of alkyl esters cannot be expressed in terms of a single regression equation. This is probably a consequence of the effect of the intramolecular hydrophobic interaction upon the retention of arylalkyl esters under GLC conditions. An analysis of the isokinetic relationships revealed…

Gas-liquid chromatography as a tool for evaluation of lipophilicity of selected esters of aromatic and aliphatic acids

Abstract The use of gas-liquid chromatographic retention values for the determination of lipophilicity was studied for series of esters of aromatic and aliphatic acids and for series of aliphatic alcohols. The regression relationships between the logarithms of the partition coefficients and the retention characteristics measured on two capillary columns, SE-30 and OV-351, differing markedly in polarity, were evaluated. It may be deduced that, for the structurally similar compounds, the stationary phases used simulate the reference partitioning system octanol-water.

Gas chromatographic separation of acetylated chlorinated phenols, guaiacols and catechols on an SE-30 quartz capillary column

Mass spectra of chlorinated aromatics formed in pulp bleaching: I—chlorinated catechols

The fragmentation of chlorinated guaiacols (2-methoxyphenols) on electron impact has been studied. The most common fragmentation processes are interpreted and in some cases the small differences between spectra of positional isomers are explained. In addition to the well-known alkyl-oxygen fission (loss of methyl radical), metastable ion studies and deuterium labelling have indicated several new fragmentation pathways. The most characteristic are the formation of [MCH3HCl]+ and [MCH3Cl]+· ions. In general, however, the spectra of positional isomers are shown to be very similar.

Gas—liquid chromatographic analyses

Abstract The gas chromatographic retention behaviour of methylethyl, 1-methylpropyl, 2-methylpropyl, 1,2-dimethylpropyl, 1-methylbutyl and 3-methylbutyl esters of benzoic and o-, m- and p-chlorobenzoic acids on low-polarity (SE-30) and polar (OV-351) capillary columns under several temperature-programmed and isothermal conditions is reported. The retention data and the Kovats retention indices for all 24 components are given and the separation of a complex mixture is discussed. The retention index increments have been used to examine the effects of chain branching and chlorine substitution. The results are compared with those for n-alkyl benzoates and monochlorobenzoates.

Glass capillary gas chromatography of methyl, methyl 2-chloro and chloromethyl esters of C2-C20n-carboxylic acids

Gas—liquid chromatographic analyses

Abstract The retention (I), dispersion (IM) and selectivity (I*) indices of sixteen polychlorinated dibenzo-p-dioxins and fourteen polychlorinated dibenzofurans were determined on a low-polarity HP-5 capillary column using a gas chromatograph connected with an ion-selective detector. IM and I* values were also calculated for all 73 dibenzo-p-dioxins from the di- to the octachloro isomer and for all possible 135 chlorinated dibenzofurans based on the predicted retention index data reported earlier. The effect of the position of chlorination is shown and the results are compared with those for several series of chlorinated aromatics.

Mass spectra of halogenated esters: 8. Methyl esters of 2,3-dichloro-, bromochloro- and dibromopropenoic acids

The mass spectral fragmentation of methyl esters of E and Z isomers of 2,3-dichloro-, 2-bromo-3-chloro-, 3-bromo-2-chIoro- and 2,3-dibromopropenoic acids have been investigated. The M+˙ peak is shown with all isomers, the [M − OCH3]+, [M − X]+, [M − OCH3 − CO]+, [M − OCH3 − CO − X]+˙ and [M − OCH3 − CO − X − X]+ ions constituting abundant peaks in all spectra. The results, particularly from the bromochloro isomers, show that a halogen atom is eliminated from the 3- rather than the 2- position and from the Z rather than the E isomer. Bromine as a bulky atom is preferentially lost.

Gas chromatography of homologous esters

Abstract The gas chromatographic retention behaviour of the butanoyl and 2-, 3- and 4-chlorobutanoyl esters of C 3 —C 5 saturated aliphatic branched-chain and unsaturated C 3 —C 6 alcohols on SE-30 and OV-351 glass capillary columns operated iso-thermally at several temperatures is reported. Retention index increments at 80, 120 and 160°C show the effects of chain branching and the olefinic and acetylenic unsaturation in the alkyl chain and the effect of the position of the chlorine substituent in the acyl chain. The results are compared with the behaviour of the corresponding n -alkyl esters and the chlorinated propanoyl esters.

Gas-liquid chromatographic analyses

A mixture of all nine chlorinated 4-hydroxybenzaldehydes and the parent homologue was separated on a non-polar SE-30 capillary column using various isothermal and temperature-programmed operating conditions. The relative retention data for the compounds are given and the retention indices together with the retention index increments for each position of chlorine substitution are examined. The retention order 3-Cl<parent<2,5-di-Cl<2,3-di-Cl<3,5-di-Cl<2-Cl<2,3,5-tri-Cl<2,3,6-tri-Cl<2,6-di-Cl<tetra-Cl isomer obtained indicates that the effect of the position of substitution on the retention behaviour is greater than that of the number of chlorine atoms. The retention is maximal with 2-Cl and 2…

Electron impact mass spectra of chlorinated methyl propanoates

The mass spectral fragmentations of all eleven chlorinated methyl propanoates have been studied. Deuterium labelling and metastable ion analysis were used to elucidate the fragmentation mechanism. The molecular ion peaks of all compounds are small, except methyl 3,3-dichloropanoate (38%). In most cases α-cleavage gives the base peak [COOCH3]+, and the loss of a chlorine atom from the molecular ion is characteristic of the 3-chloro, 3,3-dichloro and 3,3,3-trichloro compounds. Metastable ions showed the losses of small neutral molecules such as CH3OH, CH2CO, CO2 and CO from the [MCl]+ ion. α-Cleavage and the loss of Cl˙ gives an intense [MCOOCH3Cl]+˙ peak, which is the base peak in the spectr…

Metastable ion studies. 4—mass spectral fragmentation and isomerization in the esters of chlorinated propenoic acids

Metastable peaks have been used to study the fragmentation pathways of the methyl and trideuteriomethyl chloropropenoates and chloromethyl propenoate. The molecular ion peaks of the unsaturated esters are more intense than those of the saturated esters, α-Cleavage, [MOCH3]+, produces the base peak in almost all compounds, the relative abundances of the additional peaks being low for chloromethyl propenoate. The losses of H2O, CH3. and COOH. indicate the isomerization of some ionized chloro esters to the chlorinated 2-butenoic acid molecular ions. An intense loss of H2O observed for methyl 2-chloropropenoate indicates its most facile isomerization, [ester]+˙ → [acid]+˙, whereas the isomeriza…

Mass spectra of chlorinated veratroles (1,2-dimethoxybenzenes)

The behaviour of all nine chlorinated veratroles (1,2-dimethoxybenzenes) under electron impact has been investigated. The most common fragmentation processes are interpreted using metastable ion analysis and deuterium labelled compounds. For all compounds studied, the most common fragmentation route seems to be the primary loss of a methyl radical followed by loss of carbon monoxide. The ion formed has a well-known quinonoid structure and fragments by several routes elucidated by metastable ion analysis. In general, the spectra of the positional isomers are shown to be practically similar and it is apparent that e.g. the 3- and 4-chloro isomers can be differentiated only from the abundance …

Gas—liquid chromatographic analyses

Abstract The gas chromatography (GC) of n -alkyl acetates (CH 3 COOR), chloroacetates (CH 2 ClCOOR), dichloroacetates (CHCl 2 COOR) and trichloroacetates (CCl 3 COOR), where the alcohol chain length (R) varied between 1 and 8, and certain of their monochlorinated derivatives, 176 compounds altogether, has been studied on SE-30 and OV-351 glass capillary columns under the same operating conditions. The isomeric monochlorinated esters are eluted in direct order from the 1- chloro to the ω-chloro isomer, the separation of the isomers being complete on OV- 351. On SE-30, however, the peaks of the 6- and 7-chlorooctyl esters are partly overlapped. The separation of the mixtures of odd- and e…

Mass spectra of methoxychlorobenzenes (chloroanisoles)

Electron impact mass of all 19 ring-substituted chloroanisoles have been investigated. The fragmentation pathways were elucidated with the aid of the 1st field-free region metastable ions. The greatest disparity between the spectra of the positional isomers is shown with the [M−CH 3 ] + and [M−CH 2 O] +• ions, i.e., the ortho and para isomers preferentially lose • CH 3 , whereas the meta isomers generally show both loss of • CH 3 and elimination of formaldehyde, the latter process being more dominant with the meta-monochloro and di- and trichloro isomers having two meta-chlorine atoms. Characteristic for all isomers is also the abundant M +• and [M−CH 3 −CO] + ions, the other fragmentation …

1H NMR and IR spectra of methyl dichloropropanoates and butanoates

Abstract Methyl dichloropropanoates and butanoates were synthesized and their 1H NMR and IR spectra were studied. Comparisons were made with the spectral characteristics of corresponding monochlorocompounds. Special attention was given to the elucidation of the characteristic spectral features associated with particular chlorine substitution patterns. The 1H NMR of erythro and threo methyl 2,3-dichlorobutanoates were analyzed using a computer program MAOCON, a modified LAOCOON 3 program. In the spectrum of the threo form the order of the chemical shifts of protons on asymmetric carbons seems to be opposite to that reported in earlier literature. Also vicinal coupling constants J23 were foun…

Mass spectra of halogenated esters 5—Chloromethyl esters of aliphatic C2C12n-carboxylic acids and their monochlorinated derivatives

A study has been made of the mass spectral fragmentation upon electron impact of aliphatic C2C12 chloromethyl esters and all their 66 monochlorinated derivatives. The fragmentation pathways of the parent chloromethyl esters were elucidated with the aid of the 1st FFR metastable ions. A McLafferty rearrangement gives the base peak in the C6C11 parent esters and in almost all the 4-chloro and ω-chloro isomers. The subsequent loss of HCl gives a very characteristic peak of the chloromethyl esters and their (3-ω)-chloro derivatives at m/z 72, [C3H4O2]+. The 2-chloro isomers have the corresponding chlorine-containing fragment ion at m/z 106/108. The mass spectra of 2-, 3-, 4-, 5- and ω-chloro is…

Gas-liquid chromatographic analyses

Abstract The gas chromatography of mixtures of n -alkyl acetates (CH 3 COOR, R = C 1 —C 8 ) and methyl esters of aliphatic n -carboxylic acids (R′COOCH 3 , R′ = C 1 —C 8 ) and certain of their monochlorinated derivatives has been studied on Carbowax 20M and SE-30 glass capillary columns under the same operating conditions. The separation of the isomeric monochlorinated esters was complete on Carbowax 20M, whereas on SE-30 the peaks of 6- and 7-chlorooctyl acetates and methyl (ω − 1)- and (ω − 2)-chlorooctanoates and -nonanoates partly overlapped. The complete separation of the mixtures could not be achieved, however, on Carbowax 20M, in spite of the use of various operating conditions. The …

Retention increments of isomeric chlorobenzenes

The chlorobenzene isomers are used extensively as intermediates in a wide range of chemical products. More recently their determination in environmental situations has become of considerable importance and chromatographic procedures have been widely reported for their determination in both trace and major amounts. There are over 220 publications in which gas chromatography (GC) has been applied to the analysis of chlorobenzene. However, over 60 o/o of these works refer to the separation of only one isomer. Relatively few publications’-8 consider all the isomers, although the use of both capillary3’ and packedcolumns with polar and non-polar stationary phases has been reported. Temperature p…

Mass spectra of halogenated esters. Part IX—methyl esters of 2-butenoic acids containing chlorine and/or bromine atom(s)

The electron impact mass spectra of methyl esters of chloro-, bromo-, dichloro-, bromochloro- and dibromo-2-butenoic acids (13 esters at all) have been investigated. Generally, the peaks due to the following fragments are abundant: M+·, [M OCH3]+, [M CH3OH]+·, [M X]+, [M OCH3 CO]+ or [M COOCH3]+, [M X CH3OH]+ or [M OCH3 HX]+, [M OCH3 CO HX]+, [M OCH3 X X]+ and [M OCH3 CO X X]+. Characteristic for the 2- and 4-halo isomers are the primary losses of a methyl radical and methanol, and for the 3-halo isomers the loss of X· from M+·. Disparities between the spectra of the E and Z isomers are shown, the effect of position of halogen substitution being much more pronounced, as reported previously …

The effect of chlorine substituent(s) on the primary loss of a methyl radical from chlorinated veratroles (1,2-dimethoxybenzenes)

Gas chromatography of homologous esters

Abstract The gas chromatographic retention behaviour of the propanoyl and monochloropropanoyl esters of saturated C3C5 branched-chain and unsaturated C3C6 alcohols on SE-30 and OV-351 capillary columns at several temperatures is reported. Retention index increments at 80 and 120°C show the effect of branching in the alkyl chain and also the effect of unsaturation and of its position in the chain with chlorination at the two possible positions in the acyl chain. The various incremental effects are discussed and compared with the behaviour of the corresponding n-alkyl esters.

1H,13C,17O NMR and IR spectroscopic study of all methyl chloropropanoates

1 H, 13 C and 17 O NMR chemical shifts, n J(H,H) and n J(C,H) spin-spin coupling constants and IR absorption maxima and intensities for the most characteristic bands of methyl propanoate and all eleven chloropropanoic acid methyl esters are reported

Mass spectra of halogenated esters 6—Methyl esters of some trihalogenated propanoic and butanoic acids

The mass spectral fragmentation of trihalogenated methyl esters, formed in the reactions of monochlorinated methyl propenoates and 2-butenoates with Cl2, BrCl and Br2, have been investigated. In most cases α-cleavage gives the base peak, [COOCH3]+, the peaks originating from the subsequent losses of one or two halogen atoms also being abundant. The primary loss of a halogen atom is more prominent in the C4 derivatives, Br˙ and Cl˙ being preferentially lost from the 2- and 3-positions, respectively. The McLafferty rearrangement yields in one case the base peak; the 2-halo compounds could in general be distinguished by that fragmentation. Typical for all 2-bromo-substituted methyl butanoates …

Gas-liquid chromatographic analyses of chlorination products of propionyl chloride

Abstract Photochlorination of propionyl chloride with chlorine in the liquid phase at room temperature gives all eleven chloropropionyl chlorides from the mono-to the pentachloro isomer. The process was investigated every 2 h by gas-liquid chromatography, and the products were identified and estimated as their methyl esters by comparison with model compounds. The isomer distribution of the products was studied in detail. Because the process favours the 3-position, the main components were 3-chloropropionyl chloride up to 15 h, 3,3-dichloropropionyl chloride between 15 and 29 h, 3,3,3-trichloropropionyl chloride between 29 and 56 h and pentachloropropionyl chloride after 56 h of chlorination.

13C NMR, 1H NMR and IR spectra of a series of monochloroesters of aliphatic short chain carboxylic acids

Abstract 13 C chemical shifts for 14 isomeric monochloroesters of aliphatic carboxylic acids from propanoic acid to hexanoic acid have been determined. Comparisons are made with the literature values for methyl monochloro-octanoate isomers. Substituent effects for all positions are given. Characteristic IR absorption bands are presented and comparisons are made with regard to the isomeric structure. Connections are suggested between observed trends in IR absorption frequencies and some “abnormal” chlorine substituent effects on 13 C chemical shifts. 1 H NMR spectra of these compounds are considered.

Gas chromatographic and gas chromatographic-mass spectrometric studies of acetate esters of chlorinated phenols

Gas-liquid chromatographic analyses

Gas—liquid chromatographic analyses

Abstract The gas choromatographic retention behaviour of veratrole and all nine chlorinated veratroles was studied on SE-30 and OV-351 capillary columns. Temperature programming from 100°C at 6°C min−1 and isothermal operation at 140, 160, 180 and 200°C were used. The complete separation of a mixture was obtained on SE-30, the isomers being eluted in order of their degree of chlorination. On OV-351, however, the 3,4,5-trichloro and tetrachloro isomers overlap with temperature programming, being separated at 140, 160 and 200°C. Retention indices and increments of retention indices for each position of substitution are examined and the effect of increasing temperature on retention is discusse…