Saturated Alkyl Halides

Cold concentrated sulphuric acid will remove unsaturated hydrocarbons present in saturated hydrocarbons, or alcohols and ethers present in alkyl halides. In the former case soluble sulphonated products are formed, whilst in the latter case alkyl hydrogen sulphates or addition complexes, that are soluble in the concentrated acid, are produced. 

Indoles with carbocyclic halogen or triflate substituents are potential starting materials for vinylation, arylation and acylation via palladium-catalysed pro-cesses[l]. Indolylstannanes. indolylzinc halides and indolylboronic acids are also potential reactants. The principal type of substitution which is excluded from such coupling reactions is alkylation, since saturated alkyl groups tend to give elimination products in Pd-catalysed processes. 

Removal of unsaturated hydrocarbons, of alcohols and of ethers from saturated hydrocarbons or alkyl halides by washing with cold concentrated sulfuric acid. 

Sodium (metal). Used as a fine wire or as chips, for more completely drying ethers, saturated hydrocarbons and aromatic hydrocarbons which have been partially dried (for example with calcium chloride or magnesium sulfate). Unsuitable for acids, alcohols, alkyl halides, aldehydes, ketones, amines and esters. Reacts violently if water is present and can cause a fire with highly flammable liquids. 

Reaction with Alkyl Halides The gas inlet tube is replaced by an addition funnel, and 10 ml of HMPT is added rapidly with stirring. The mixture is cooled to 10-15°, and a solution of the alkyl halide (0.1 mole) in 20 ml of THF is added dropwise over a period of 30-40 minutes. The mixture is then heated to 40° for 2-3 hours. The thick white suspension of the sodium halide is cooled and dilute cold hydrochloric acid is carefully added until the mixture is clear. The organic layer is separated, and the aqueous layer is extracted three times with 20-ml portions of ether, the ethereal extracts then being combined with the organic material. The ethereal solution is washed twice with saturated sodium chloride solution and dried. The ether and THF are removed under reduced pressure (rotary evaporator), and the alkyne is distilled. 

Alkyl halides contain a halogen bonded to a saturated, sp3-hybridized carbon atom. The C-X bond is polar, and alkyl halides can therefore behave as electrophiles. 

Alkyl halides are more easily identified than the dichloro halides. Figure 17.1 shows the mass spectra of two dichlorohexanes. Long-chain saturated halides may also lose an alkyl portion from the molecular ion, such as 15, 29, 43, 57, 71, 85, and 99 Daltons. These can be identified as halogenated compounds, but it is difficult to deduce their molecular weights without Cl or negative Cl. 

Alkyl halides can be hydrolyzed to alcohols. Hydroxide ion is usually required, except that especially active substrates such as allylic or benzylic types can be hydrolyzed by water. Ordinary halides can also be hydrolyzed by water, if the solvent is HMPA or A-methyl-2-pyrrolidinone." In contrast to most nucleophilic substitutions at saturated carbons, this reaction can be performed on tertiary substrates without significant interference from elimination side reactions. Tertiary alkyl a-halocarbonyl compounds can be converted to the corresponding alcohol with silver oxide in aqueous acetonitrile." The reaction is not frequently used for synthetic purposes, because alkyl halides are usually obtained from alcohols. 

The unusual carbon-halogen bond strength in vinyl halides compared to saturated alkyl halides has been ascribed to partial double-bond character (103, 104) coupled with increased a-bond strength (105) due to differences in... 

Another general process involves the reaction of Pd(0) species with halides or sulfonates by oxidative addition, generating reactive intermediates having the organic group attached to Pd(II) by a ct bond. The oxidative addition reaction is very useful for aryl and alkenyl halides, but the products from saturated alkyl halides often decompose by (3-elimination. The a-bonded species formed by oxidative addition can react with alkenes and other unsaturated compounds to form new carbon-carbon bonds. The... 

A type of reaction that has probably received more detailed study than any other—largely due to the monumental work of Ingold and his school—is nucleophilic substitution at a saturated carbon atom the classical displacement reaction exemplified by the conversion of an alkyl halide into an alcohol by the action of aqueous base ... 

In this discussion of nucleophilic displacement at a saturated carbon atom, interest has tended to centre on attack by nucleophilic anions Nu e, especially eOH, on polarised neutral species, especially alkyl halides, +R—Hala . In fact this general type of displacement is extremely common involving, in addition to the above, attack by non-charged nucleophiles Nu- on polarised neutral species,... 

Reference has already been made in the last chapter to the generation of carbocations, in ion pairs, as intermediates in some displacement reactions at a saturated carbon atom, e.g. the solvolysis of an alkyl halide via the SN1 mechanism. Carbocations are, however, fairly widespread in occurrence and, although their existence is often only transient, they are of considerable importance in a wide variety of chemical reactions. 

The presence of a remote C=C double bond in the alkyl halide was critical saturated analogs underwent nickel-catalyzed halogen-zinc exchange.248 It has been suggested that the double bond coordinates to the nickel atom. As a 7r-acceptor, the C=C bond removes some electron density from the metal, thus facilitating the reductive coupling (Scheme 154).246... 

The numerous straightforward examples of internal displacement reactions leading to isolable cyclic products will not be discussed here, but only, for the most part, those ionization reactions in which a cyclic intermediate or transition state is deduced from the rearranged structure of the product. A well-known example is mustard gas and other alkyl chlorides with sulfur on the /3-carbon atom. Although mustard gas is a primary and saturated alkyl chloride, its behavior is like that of a typical tertiary alkyl chloride. It reacts so fast by a first order ionization that the rate of the usual second order displacement reaction of primary alkyl halides is not measureable. Only the ultimate product, not the rate, is determined by the added reagent.228 Since the effect of the sulfur is too large to be explicable in terms of a carbon sulfur dipole or similar explanation, a cyclic sulfonium ion has been proposed as an... 

Conjugate addition.1 This base undergoes efficient 1,4-addition to a,(i-un-saturated esters to give the enolate of a (3-amino ester, which can be trapped by an alkyl halide to give a-alkyl-(3-amino esters (2) as a mixture of syn- and antiisomers (about 1 1). These esters can be converted into 3-lactams (3) by hydrolysis and dehydration (11, 449) or into a-alkyl-a,3-unsaturated esters (4) by N-quater-nization and 3-elimination on silica gel ( 75% yield). 

An electron in the circle is called the excited electron. Absorption, although at a longer wave length than saturated hydrocarbons occurs below 9.4 x 101 K cal/mole. Therefore, ethers, disulphides, alkyl halides and alkyl amines are transparent to ultraviolet light. 

Nucleophilic Reactions.—Attack on Saturated Carbon. Selected examples of the Arbusov reaction include phosphorylation of the chloroacetophenones (1) to give phosphonates, which cyclized to (2) in the presence of acid chlorides,1 formation of the azodiphosphonate (3) from 2,2 -dichloro-2,2 -azopropane,2 3 and the reaction of 2-chloro-3,4-dihydro-3-oxo-2//-l,4-benzothiazine (4) with triethyl phosphite to give the 2-phosphonate (5), which is used as an olefin synthon.8 Bis(trimethylsilyl) trimethylsiloxymethylphosphonite (6) has been synthesized by silylation of hydroxy-methylphosphonous acid, and, as expected, undergoes a normal Arbusov reaction with alkyl halides to give the phosphonates (7).4 This series of reactions, followed by... 

Delepine reaction org chem Slow ammonolysis of alkyl halides in acid to primary amines in the presence of hexamethylenetetramine. del-3,pTn re,ak-sh3n deliquescence phys chem The absorption of atmospheric water vapor by a crystalline solid until the crystal eventually dissolves into a saturated solution. del-3 kwes-3ns ... 

Alkylation of saturated 5(4//)-oxazolones at C-4 is a well-known reaction that can be achieved under a wide variety of conditions. Numerous articles have described this reaction as a means to prepare 4,4-dialkyl-5(477)-oxazolones 147 that are valuable intermediates to prepare ot,ot-disubstituted a-amino acids. For instance,2-phenyl-5(4//)-oxazolone 146 readily obtained from hippuric acid and A,A -dicyclohexylcarbodiimide (DCC), is alkylated at C-4 with allyl, benzyl, or phenacyl halides if the reaction is conducted in dipolar aprotic solvents in the presence of weak bases. Hydrolysis of the resulting 5(477)-oxazolones leads to a,a-dialkylglycines 148 (Scheme 7.43). 

DDD Dichloro(chlorophenyl)-bis Ethane DDE Dichlorodiphenyldichloroethylene Dichlorobenzene, 1,2 Dichlorobenzene, 1,3 Dichlorobenzene, 1,4 Hexachlorobenzene Polychlorinated Benzenes Polychlorinated Biphenyls PCBs Aroclor Ring-Substituted Aromatics Tetrachlorobenzene Trichlorobenzene, 1,2,4 Saturated Alkyl Halides Bromodichloromethane Bromoform Tribromomethane Butyl Chloride Chlorobutane Carbon Tetrachloride Carbon Tetrafluoride Chloroform Trichloromethane Chloromethane Methyl Chloride Dibromochloromethane Dibromoethane, 1,2 Ethylene Dibromide Dibromomethane... 

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