Hydrogen halides alcohols

I. Reaction with hydrogen halides Alcohols react with hydrogen halides to form alkyl halides (Refer Unit 10, Class Xll). [Pg.61]

In these compounds the carbon atom is mostly negative and the phosphorus is positive polarized, thus in the case of an addition of proton-active reagents such as hydrogen halides, alcohols, or amines the proton moves to the carbon and the anionic part moves to the phosphorus atom [Eq. (12)] (8,14). [Pg.269]

The order of acid reactivity is hydrogen halides > alcohol, thiols > amines. It is noteworthy that (GeH3)3P is inert to H O cleavage but reacts rapidly with H S ... [Pg.56]

Lewis acids are seldom effective sdone rather they require the presence of trace amounts of water or some other proton donor (protogen) such as hydrogen halide, alcohol, and carboxylic acid, or a carbocation donor (cationogen) such as t-butyl chloride or triphenylmethyl chloride, which, on reaction with the Lewis acid, forms the electrophilic species that initiates polymerization. Thus dry isobutylene is unaffected by dry boron trifluoride but polymerization occurs immediately when trace amounts of water are added. The initiation process for boron trifluoride and water is... [Pg.707]

The condensation of acetylenes with carbon monoxide, hydrogen halides, alcohols, acids, amines, mercaptans, halogens, etc., gives extremely useful unsaturated compounds as generalized by Eq. (6). [Pg.17]

Other catalysts which may be used in the Friedel - Crafts alkylation reaction include ferric chloride, antimony pentachloride, zirconium tetrachloride, boron trifluoride, zinc chloride and hydrogen fluoride but these are generally not so effective in academic laboratories. The alkylating agents include alkyl halides, alcohols and olefines. [Pg.509]

The major portion of the present chapter concerns the conversion of alcohols to alkyl halides by reaction with hydrogen halides... [Pg.142]

Preparation of Alkyl Halides from Alcohols and Hydrogen Halides... [Pg.151]

PREPARATION OF ALKYL HALIDES FROM ALCOHOLS AND HYDROGEN HALIDES... [Pg.151]

The order of reactivity of the hydrogen halides parallels their acidity HI > HBr > HCl >> HF Hydrogen iodide is used infrequently however and the reaction of alco hols with hydrogen fluoride is not a useful method for the preparation of alkyl fluorides Among the various classes of alcohols tertiary alcohols are observed to be the most reactive and primary alcohols the least reactive... [Pg.152]

Increasing reactivity of alcohols toward hydrogen halides... [Pg.152]

Secondary and pnmary alcohols do not react with HCl at rates fast enough to make the preparation of the conespondmg alkyl chlorides a method of practical value There fore the more reactive hydrogen halide HBr is used even then elevated temperatures are required to increase the rate of reaction... [Pg.152]

The reaction of an alcohol with a hydrogen halide is a substitution A halogen usually chlorine or bromine replaces a hydroxyl group as a substituent on carbon Calling the reaction a substitution tells us the relationship between the organic reactant and its prod uct but does not reveal the mechanism In developing a mechanistic picture for a par ticular reaction we combine some basic principles of chemical reactivity with experi mental observations to deduce the most likely sequence of steps... [Pg.153]

As carbocations go CH3" is particularly unstable and its existence as an inter mediate m chemical reactions has never been demonstrated Primary carbocations although more stable than CH3" are still too unstable to be involved as intermediates m chemical reactions The threshold of stability is reached with secondary carbocations Many reactions including the reaction of secondary alcohols with hydrogen halides are believed to involve secondary carbocations The evidence m support of tertiary carbo cation intermediates is stronger yet... [Pg.160]

Reaction of Primary Alcohols with Hydrogen Halides The Sn2 Mechanism... [Pg.163]

The SnI mechanism is generally accepted to be correct for the reaction of tertiary and secondary alcohols with hydrogen halides It is almost certainly not correct for methyl alcohol and primary alcohols because methyl and primary carbocations are believed to be much too unstable and the activation energies for their formation much too high for them to be reasonably involved The next section describes how methyl and primary alcohols are converted to their corresponding halides by a mechanism related to but different from S l... [Pg.163]

REACTION OF PRIMARY ALCOHOLS WITH HYDROGEN HALIDES THE Sn2 MECHANISM... [Pg.163]

The first step of this new mechanism is exactly the same as that seen earlier for the reaction of tert butyl alcohol with hydrogen chloride—formation of an alkyloxonmm ion by proton transfer from the hydrogen halide to the alcohol Like the earlier exam pie this IS a rapid reversible Brpnsted acid-base reaction... [Pg.164]

It IS important to note that although methyl and primary alcohols react with hydro gen halides by a mechanism that involves fewer steps than the corresponding reactions of secondary and tertiary alcohols fewer steps do not translate to faster reaction rates Remember the order of reactivity of alcohols with hydrogen halides is tertiary > sec ondary > primary > methyl Reaction rate is governed by the activation energy of the slowest step regardless of how many steps there are... [Pg.165]

Secondary and tertiary alcohols react with hydrogen halides by a mech anism that involves formation of a carbocation intermediate m the rate determining step... [Pg.179]

Reactions of alcohols with hydrogen halides (Section... [Pg.180]

Alcohols react with hydrogen halides to yield al kyl halides The reaction is useful as a synthesis of al kyl halides The reactivity of hydrogen halides de creases in the order HI > HBr > HCI > HF Alcohol re activity decreases in the order tertiary > secondary > primary > methyl... [Pg.180]

Section 4 9 The potential energy diagrams for separate elementary steps can be merged into a diagram for the overall process The diagram for the reac tion of a secondary or tertiary alcohol with a hydrogen halide is charac terized by two intermediates and three transition states The reaction is classified as a ummolecular nucleophilic substitution, abbreviated as SnI... [Pg.180]

Primary alcohols do not react with hydrogen halides by way of carbo cation intermediates The nucleophilic species (Br for example) attacks the alkyloxonium ion and pushes off a water molecule from carbon m a bimolecular step This step is rate determining and the mechanism is Sn2... [Pg.181]

The dehydration of alcohols resembles the reaction of alcohols with hydrogen halides (Section 4 7) m two important ways... [Pg.206]

These common features suggest that carbocations are key intermediates m alcohol dehydra tions just as they are m the reaction of alcohols with hydrogen halides Figure 5 6 portrays a three step mechanism for the acid catalyzed dehydration of tert butyl alcohol Steps 1 and 2 describe the generation of tert butyl cation by a process similar to that which led to its for matron as an intermediate m the reaction of tert butyl alcohol with hydrogen chloride... [Pg.206]

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