Ethyl chloride, ionic reactions

Addition. Vinyl chloride undergoes a wide variety of addition reactions. Chlorine adds to vinyl chloride to form 1,1.2-tnchloroethane by either an ionic or a radical path. Hydrogen halides add to vinyl chloride, usually to yield the 1.1-adduct. Many other vinyl chlonde adducts can be formed under acid-catalyzed Fnedel-Crafts conditions. Vinyl chloride can be hydrogenated to ethyl chloride and ethane over a platinum on alumina catalyst. 

Excision reactions are sometimes accompanied by redox chemistry. For example, dissolution of the 2D solid Na4Zr6BeCli6 in acetonitrile in the presence of an alkylammonium chloride salt results in simultaneous reduction of the cluster cores (144). Here, the oxidation product remains unidentified, but is presumably the solvent itself. As a means of preventing such redox activity, Hughbanks (6) developed the use of some room temperature molten salts as excision media, specifically with application to centered zirconium-halide cluster phases. A number of these solids have been shown to dissolve in l-ethyl-2-methylimidazolium chloride-aluminum chloride ionic liquids, providing an efficient route to molecular clusters with a full compliments of terminal chloride ligands. Such molten salts are also well suited for electrochemical studies. 

Several recent publications indicate that the role of intermediate complexes in ionic reactions is still controversial (21, 24, 25). Our interest in this and earlier observations of persistent complexes in alkyl halides already mentioned prompted us to study ionic reactions in ethyl chloride. The previously noted mass spectrometric investigations of alkyl halides did not include the chlorides, and radiolytic studies of these compounds have been limited to the propyl and butyl chlorides which apparently isomerize (39). The present investigation consists of two phases. In the initial phase, the ion-molecule reactions for ethyl chloride were probed by the sensitive mass spectrometric methods which we have applied in recent studies of a similar nature (3,12, 28, 43). In the latter part of this study, the gas-phase radiolysis and vacuum-ultraviolet photolysis of ethyl chloride have been studied to identify those products which arise from ionic precursors. More specifically, we wished to define the behavior under radiolytic conditions of those intermediate ionic species which the spectrometric studies suggested were important, and we hoped to arrive at a reasonable conciliation of the ionic reaction information derived from these different but complementary techniques. 

It is also of interest to consider possible further reactions with ethyl chloride of the secondary ionic products from these processes. For C2H6C1+, the cross section for Reaction 5a is large enough to permit production of this ion in reasonable abundance even at the comparatively low pressures possible in the first stage of the tandem spectrometer hence, it was possible to observe the reaction of this ion directly. As Reaction 6 shows, this leads to a condensation product which loses a molecule of HC1 ... 

A striking feature of the ionic reaction scheme for ethyl chloride which is evident from examining the reactions above is the fact that virtually all of these processes lead either to the protonated molecule ion or to other precursors of this product. In addition, the protonated species is efficiently converted to the C4Hi0C1+ ion hence, one expects that at higher pressures there will be essentially only this one ionic species present in any appreciable quantity. This conclusion is also supported by the high pressure mass spectrometer data discussed below. 

Implications of Mass Spectrometric Data for Radiation Chemistry. Apart from the positive identification of the ion-molecule reactions in ethyl chloride, the most significant observation from the mass spectrometric studies which has direct application to the radiolysis of this compound is the fact that at pressures greater than ca. 100 /a, essentially the only stable ion in this system is C4Hi0C1+. Therefore, the neutralization of ions as a potential contributor to radiolysis products will be important only for this ion. Moreover, this will hold true even if there are variations in the extent of primary fragmentation with increasing pressure. The radiolysis studies which will now be described assess the contribution of ionic processes to radiolytic yields and provide some indications as to the mode of neutralization of the stable ionic species in the ethyl chloride system. 

Table III also shows that hydrogen and the chlorinated butanes are reduced substantially when ethyl chloride is irradiated in the presence of benzene. The other products are essentially unaffected by this additive. In the radiolysis of certain alkanes (4), benzene, added in small amounts, does not interfere with the fast ion-molecule reactions of primary ionic fragments or with free radical processes, but it will efficiently condense unreactive or long-lived ions in the system. It is reasonable to assume that this is also true for alkyl halide systems and that the reduction in product yields compared with the pure compound upon adding benzene may be attributed to the interception of unreactive ions. Since the rate constants for reactions of the expected primary ions with ethyl chloride are very large (see Table II), the concentration of benzene used in our experiments should not interfere with the initial fast ion-molecule reactions. For ethyl chloride ion-molecule reactions, C4Hi0C1+ is the only unreactive ion of appreciable abundance which is expected in this system at the elevated pressures used in the radiolysis experiments. Thus, the reduced product yields in the presence of benzene additive can be identified tentatively with the removal of this stable ion and the elimination of its resultant neutralization products.

The radiolysis product yields in the presence of ion scavenger (Table III) also show that ethane is not formed from neutralization of stable ions. Therefore, the remainder of the ethane product (above that indicated to result from neutral decomposition) must be produced by an ion-molecule process—i.e., a yield of G = 1.47. The ion-molecule reactions previously listed show that ethylene ions react with ethyl chloride to form ethane. From the relative rates indicated for Reactions 3a-3d and the ethane yield just derived, a relative yield of 2.46 may be deduced for the ionic fragmentation to ethylene ion in the radiolysis. 

Ionic reactions in ethyl chloride have been studied by both mass spectrometric and radiolysis techniques. The radiolysis mechanism advanced on the basis of our experimental observations indicates that the major radiolytic reaction mode in this system is excited neutral molecule decomposition. While the role of ionic reactions in the radiolysis therefore appears to be relatively minor, it was possible to establish a good correlation between the predictions of the mass spectrometric studies with respect to ionic intermediates and the participation of such ions in the radiolytic reaction scheme. These results emphasize the advantages of combining the techniques used here to obtain a complete description of the reactive system. 

It is known that triethyl phosphite reacts with carbon tetrachloride to give ethyl chloride and diethyl (trichloroethyl)phosphonate. Ionic and radical mechanisms have been suggested to account for this remarkable reaction. According to the most reasonable, fundamental one (61), the reaction is initiated by a nucleophilic attack on chlorine (not an Arbusov reaction) followed by formation of the phosphonium salt [71] (Atkinson et al., 1969). 

Geometrical trans to cis isomerization of 3,3 -, 4,4 -, and 5,5 -disubstituted 2,2 -diphenoquinones has been studied by computational methods.The double bond isomerization of butene-catalysed l-ethyl-3-methyl-imidazolium chloride ionic liquid has been similarly examined and stepwise isomerization is suggested.The reaction of l,2-di(l-adamantyl)-2-thioxoethanone with diazomethane and 2-diazopropane gave 2-acylthiiranes via 2 - - 3-cycloaddition, elimination of nitrogen, and 1,3-dipolar electrocyclization of the intermediate acyl-substituted thiocarbonyl ylides. Rearrangement of pyrimidine-5-carboxylic acids esters to 5-acylpyrimidones does not occur in the examples studied and a [l,4]-phospho-Fries rearrangement has been reported. ... 

Recently several pubhcations have examined replacing aqueous solvents with ionic liquids. Since simple and complex sugars are soluble in many imidazolium hahdes, water is not required as a co-solvent and degradation of HMF is minimal. Lansalot-Matras et al. reported on the dehydration of fmctose in imidazolium ionic liquids using acid catalyst (6). Moreau et al. reported that l-H-3-methylimidazolium chloride has sufficient acidity to operate without added acid (7). And we reported that a 0.5 wt% loading (6 mole% compared to substrate) of many metal halides in 1-ethyl-3-methylimidazohum chloride ([EMIM]C1) result in catalytically active materials particularly useful for dehydration reactions (8). 

The synthesis and some reactions of meso-ionic 1,2-dithioM-ones (388) have been recently reported. The brown compound 388, R = R = Ph, has been prepared by several methods (i) the reaction betw i l,l,3,3-tetrabromo-l,3-diphenylacetone (PhCBrjCOCBrjPh) and potassium ethyl xanthate, (ii) the reaction between 1,3-diphenyl-propanetrione hydrate and tetraphosphorus decasulfide, (iii) 1,3-diphenylpropanetrione with hydrogen sulfide-hydrogen chloride in ethanol-chloroform yields the salt 389, R = R = Ph, X = Cl, which gives the meso-ionic I,2-dithiol-4-one with triethylamine, pyridine, or aqueous sodium bicarbonate. ... 

Campbell, J. L. E., Johnson, K. E., and Torkelson, J. R., Infrared and variable-temperature H-NMR investigations of ambient-temperature ionic liquids prepared by reaction of HCl with l-ethyl-3-methyl-lH-imidazolium chloride, Inorg. Chem., 33, 3340,1994. 

Seddon showed that l-ethyl-3-methyl imidazolium chloride-aluminum(lll) chlorides are ionic liquids at temperatures as low as -90°C (Seddon, 1996 Earle and Seddon, 2000). These nonvolatile ionic liquids can solvate a wide range of organic reactions including oligomerisations, polymerizations (Lynn et al., 2000), alkylations (Ross et al., 2001), and acylations (Seddon, 1997 Welton, 1999). 

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