Alkyl halides reaction with water

The El reaction involves the formation of a planar carbocation intermediate. Therefore, both syn and anti elimination can occur. If an elimination reaction removes two substituents from the same side of the C—C bond, the reaction is called a syn elimination. When the substituents are removed from opposite sides of the C—C bond, the reaction is called an anti elimination. Thus, depending on the substrates El reaction forms a mixture of cis (Z) and trans (E) products. For example, tert-hutyl bromide (3° alkyl halide) reacts with water to form 2-methylpropene, following an El mechanism. The reaction requires a good ionizing solvent and a weak base. When the carbocation is formed, SnI and El processes compete with each other, and often mixtures of elimination and substitution products occur. The reaction of t-butyl bromide and ethanol gives major product via El and minor product via SnI-... 

The scope of the reactions of phosphazenes with alkyl halides and, subsequently, water, as a preparative route to secondary amines (as their hydrohalides) has been investigated ... 

As in the case with the other members of group IVA, the mixed alkyl and aryl halides of lead are also known, and their reactions with water, alcohols, amines, and other organic compounds can be used to prepare a large number of other derivatives. 

The basic hydrolysis (reaction with water) of a nitrile (R-CN) followed by acidification yields a carboxylic acid. In general, an reaction (nucleophilic substitution) of an alkyl halide is used to generate the nitrile before hydrolysis. Figure 12-12 illustrates the formation of a carboxylic acid beginning with an alkyl halide. 

It has been shown that phenylselenyl halides easily reacted with 0-allyl oximes 221 to give cyclic iminium salts 222, which by reaction with water afforded isoxazolidines 223 in moderate to good yields (equation 96) . Compounds 222 can be reduced in situ by sodium borohydride to produce Ai-alkyl-substituted isoxazolidines 224 in 50-95% yields . ... 

The dialkylzincs up to the dibutyl derivatives readily ignite and bum in air. The higher alkyls fume but do not always ignite [1]. During preparation of dialkylzincs, reaction of the copper—zinc alloy with mixed alkyl bromides and iodides must begin (exotherm, often after a long induction period), before too much halide mixture is added, or violent explosions may occur [2]. Reactions with water may be explosive [3]. 

Strong nucleophiles such as organolithium or organomagnesium derivatives do not react with substituted or unsubstituted phosphabenzene or arsabenzene (39, Y = P or As) by nucleophilic substitution as in the case of pyridines, but by addition to the heteroatom forming intermediate anions 40. These can then be converted into nonaromatic compounds by reaction with water to yield 1-alkyl-1,2-dihydro-derivatives 41, or they can be alkylated by an alkyl halide with the same or a different alkyl group, when two products may result a 1,2-dialkyl-1,2-dihydro 40-derivative 42, or a -derivative 43. The former products are kinetically controlled, whereas the latter compounds are thermodynamically controlled, so that one may favor the desired product by choosing the appropriate reaction conditions. 

Similar information is available for other bases. Lithium phenoxide (LiOPh) is a tetramer in THF. Lithium 3,5-dimethylphenoxide is a tetramer in ether, but addition of HMPA leads to dissociation to a monomer. Enolate anions are nucleophiles in reactions with alkyl halides (reaction 10-68), with aldehydes and ketones (reactions 16-34, 16-36) and with acid derivatives (reaction 16-85). Enolate anions are also bases, reacting with water, alcohols and other protic solvents, and even the carbonyl precursor to the enolate anion. Enolate anions exist as aggregates, and the effect of solvent on aggregation and reactivity of lithium enolate anions has been studied. The influence of alkyl substitution on the energetics of enolate anions has been studied. ... 

Alkyl thiocyanates (39) are prepared by heating alkyl halides ortosylates with sodium or potassium thiocyanate (Scheme 21). The reaction may be performed in acetone, ethanol or water, but goes best in polar aprotic solvents like DMF or DMSO. The thiocyanate ion is an ambidentate nucleophile owing to resonance (Figure 1).4 In principle, therefore, the reaction shown in Scheme 21 may yield... 

Organolithium and Grignard reagents are prepared from alkyl (or aryl) halides. The reactions are carried out under anhydrous conditions because reaction with water leads to the formation of alkanes. 

It will be recalled that the alkyl halides enter into reaction with water but slowly, and that heating to a high temperature is required to effect the interchange of chlorine and hydroxyl with an appreciable speed. 

In the previous chapters the preparation and properties of certain important classes of compounds have been discussed, and the principles which are illustrated in their transformations into one another have been emphasized. These principles are of wide application and can be employed in the preparation of compounds of more complex structure than any met with so far. For example, the method of preparing an alcohol by the treatment of an alkyl halide with water or an alkali, is very general in its application. The reaction consists in the replacement of a halogen atom by a hydroxyl group, and such replacement takes place not only with alkyl halides, but with other compounds which contain halogen. Thus, chloroacetic acid can be transformed into hydroxyacetic acid by water —... 

In solvents such as water and alcohols, fluoride ion is strongly solvated by ion-dipole forces and is neither very basic nor very nucleophilic. On the other hand, the poorly solvated, or naked, fluoride ions that are present when potassium fluoride dissolves in benzene in the presence of a crown ether are better able to express their anionic reactivity. Thus, alkyl halides react with potassium fluoride in benzene containing 18-crown-6, thereby providing a method for the preparation of otherwise difficultly accessible alkyl fluorides. No reaction is observed in the absence of the crown ether. 

The step of cationic initiation can be subdivided into two separate reactions. The first one consists of formation of ionic species and the second one of reactions of these ionic species with the olefins, a cationization process. This reaction, termed priming by Kennedy and Marechal, is a process of ion formation in a non-nucleophilic media through (1) dissociation of protonic acids to form protons and counterions, (2) reactions of Lewis acids with Bronsted acids, (3) dissociation of dimeric Lewis acids, (4) complexation of Lewis acids with water or with alkyl halides or with ethers, and so on. These reactions may take place through a series of complicated steps. The second reaction, the cationization of the olefins, may also include several intermediate steps that will eventually lead to propagating species. 

Friedel-Crafts Alkylation and Acylation Reactions. Alcohols and alkyl halides react with aromatics in the presence of gallium triflate to give the corresponding alkylated products. Since Ga(OTf)3 does not decompose in the presence of water, alcohols can be used as good alkylating agents. Alkylation of benzene... 

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