Halide alkyl

Alkyl halide R X —X X = F,C1, Br, 1 CH3CI CH3CH2CI chloromethane chloroethane methyl chloride ethyl chloride 

Alcohol ROH — OH CH3OH CH3CH2OH methanol ethanol methyl alcohol ethyl alcohol 

Ether R-O-R R—0—R CH3—0—CH3 CH3CH2—0—CH2CH3 methoxymethane ethoxyethane dimethyl ether diethyl ether 

Carboxylic acid R-C ° OH -cf OH HCOOH CH3COOH methanoic acid ethanoic acid formic acid acetic acid 

Ester R—c f OR OR HCOOCH3 CH3COOCH3 methyl methanoate methyl ethanoate methyl formate methyl acetate 

Alkyl halides have the general formula RX, where R is an alkyl or substituted alkyl group and X is any halogen atom (F, Cl, Br, or 1). 

Problem 7.1 Write structural formulas and lUPAC names for all isomers of (a) C HuBr. Classify the isomers as to whether they are tertiary (3°), secondary (2°), or primary (1°). (b) C H Clj. Classify the isomers which are gem-dichlorides and vic-dichlorides.  

Take each isomer of the parent hydrocarbon and replace one of each type of equivalent H by X. The correct lUPAC name is written to avoid duplication. 

Classification is based on the structural features RCHjBr is 1°, R CHBr is 2°, and RjCBr is 3° From isopentane, (CH3)2CHCH2CH, we get four isomers. 

Neopentane has 12 equivalent H s and has only one monobromo substitution product, (CH3),CCH2Br (1°), l-bromo-2,2-dimethylpropane. 

In alkyl halides the hydrogen (the one attached to the same carbon as the halogen) wUl be deshielded. 

In alcohols, both the hydroxyl proton and the a hydrogens (those on the same carbon as the hydroxyl group) have characteristic chemical shifts. 

C-OH 0.5-5.0 ppm The chemical shift of the —OH hydrogen is variable, its position depending on concentration, solvent, and temperature. The peak may be broadened at its base by the same set of factors. 

CH-O-H 3.2-3.S ppm Protons on the a carbon are deshielded by the electronegative oxygen atom and are shifted downfield in the spectrum. 

CH-OH No coupling Because of the rapid chemical exchange of the —OH proton in 

Hydrogens attached to the same carbon as a halogen are deshielded (local diamagnetic shielding) due to the electronegativity of the attached halogen (Section 5.11A). The amount of deshielding 

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Other Substrates.—Alkyl Halids, The reaction of tritium atoms of initial energy 160—320kJmol with CH3F has been examined/ and CH3T and CH2FT determined relative to HT. Yields for T-for-F substitution are higher than those for T-for-H substitution, and the threshold for replacement of F( 130 kJ mol ) is about SO U mol lower than that for replacement of H. 

Photolysis at 298 nm of HI mixed with CH3O or CHsBr yidds CH4 as a result of the attraction and substitution reactions (71) and (72). The sum of the integral reaction probabilities of reactions (71) and (72) for atoms of initial energy 

109 kJ mol is 0.06 0.01 for X = Q and 0.27 0.04for X = Br. The net probability of D abstraction from CDsBr at the same energy is about 0.03. Much higher net probabilities of chlorine abstraction or replacement than in CHsCl are observed at the same energy for polychloromethanes.  

Methanethiol. The reaction of H with CHsSH is similar to that with CH3CI or CHsBr. The sum of the net probabilities of processes (75) and (76) is 0.114 0.013 

Using alkyl halides the scope of the reaction is limited to benzylic compounds unless one uses stoichiometric amounts of the versatile Collman reagent Na2pe(CO)4 (Table II). 

Starting material Product Catalyst Conditions C bar Yield (%) Ref. 

Anodic oxidation of alkyl iodides in acetonitrile has been studied, cycloheptyl iodide gave N-cycloheptylacetamide. The complex base NaNH2 Bu OK is capable of effecting syn-eliminations, e.g. rrons-l,2-dibromocycloheptane gave 1-bromocycloheptene in 90% yjeld.  

Alcohols, Thiols, Esters.—Direct spectroscopic determination of the absolute configuration of a hydroxyl bearing asymmetric centre based on the sign of the induced 

Solvolysis rates of tertiary systems where a methyl group is present, have been used to estimate the rate of solvolysis of the corresponding secondary compounds good agreement was obtained between predicted and observed solvolysis rates for several systems which involved nucleophilic solvent assistance. Solvolysis in 60% aqueous acetone of the 3,5-dinitrobenzoate esters of cycloalk-2-en-l-ols labelled with deuterium at the 1-position, showed that little scrambling of the label or racemization occurred in the cyclo-octenol case, ca. 33 % scrambling occurred in the cycloheptenol case, and 56% scrambling occurred in the cyclohexenol case. Therefore, allylic participation, especially in the cyclo-octenol case, was rather weak.  

Exclusive cleavage of the cycloalkyl carbon-oxygen bond occurs on treatment of cycloalkyl methyl and ethyl ethers with acetyl chloride in the presence of a Lewis acid catalyst. 

Cyclic Ketones.—Whereas treatment of 2,6,6-trimethylcyclohepta-2,4-dienone in DMSO with oxygen in the presence of base and treatment of 3,7,7-trimethylbicyclo-[4,l,0]hept-3-en-2,5-dione with a base in DMSO gave semidione (306X treatment of 

Key point. Alkyl halides are composed of an alkyl group bonded to a halogen atom (X = F, Cl, Br, I). As halogen atoms are more electronegative than carbon, the C-X bond is polar and nucleophiles can attack the slightly positive carbon atom. This leads to the halogen atom being replaced by the nucleophile in a nucleophilic substitution reaction, and this can occur by either an SN1 (two-step) mechanism or an Sn2 (concerted or one-step) mechanism. In competition with substitution is elimination, which results in the loss of HX from alkyl halides to form alkenes. This can occur by either an El (two-step) mechanism or an E2 (concerted) mechanism. The mechanism of the substitution or elimination reaction depends on the alkyl halide, the solvent and the nucleophile/base. 

Alkyl halides have an sp3 carbon atom and hence have a tetrahedral 

RELATIVE RATES OF PYROLYTIC ELIMINATION OF SOME ALKYL SUBSTRATES. 

From a kinetic standpoint, this field has been extensively studied and reviewed by MaccolE - . Heterogeneous reactions, which give irreproducible kinetics, can be minimised by the use of seasoned vessels and the rigid ex- 

A more detailed analysis of the radical mechanisms has been presented . Generally, all three processes show first-order kinetics but Ej reactions do not exhibit an induction period and are unaffected by radical inhibitors such as nitric oxide, propene, cyclohexene or toluene. For the non-chain mechanism, the activation energy should be equivalent to the homolytic bond dissociation energy of the C-X bond and within experimental error this requirement is satisfied for the thermolysis of allyl bromide For the chain mechanism, a lower activation energy is postulated, hence its more frequent occurrence, as the observed rate coefficient is now a function of the rate coefficients for the individual steps. Most alkyl halides react by a mixture of chain and E, mechanisms, but the former can be suppressed by increasing the addition of an inhibitor until a constant rate is observed. Under these conditions a mass of reliable reproducible data has been compiled for Ej processes. Necessary conditions for this unimolecular mechanism are (a) first-order kinetics at high pressures, (b) Lindemann fall-off at low pressures, (c) the absence of induction periods and the lack of effect of inhibitors and d) the absence of stimulation of the reaction in the presence of atoms or radicals. 

For a quasi-heterolytic transition state, substituent effects in pyrolytic reactions should simulate those observed in El reactions, whereas for a homolytic transition state a resemblance to effects noted in known homolytic processes is expected. The experimental facts strongly support the former suggestion. 

Although alpha methyl substitution markedly influences the rates of pyrolysis of alkyl halides, it has virtually no effect on the homolytic decomposition of cyclobutane cf. 158 and Table 25) -.  

The important chemistry of alkyl halides, RX, includes the nucleophilic (SN) displacement and elimination (E) reactions discussed in Chapter 8. Recall that tertiary alkyl halides normally are reactive in ionization (SN1) reactions, whereas primary halides, and to a lesser extent secondary halides, are reactive in Sn2 reactions, which occur by a concerted mechanism with inversion of configuration (Sections 8-4 to 8-7). 

Elimination competes with substitution in many SN- reactions and can become the major pathway at high temperatures or in the presence of strong base. Elimination (E2), unlike displacement (SN2), is insensitive to steric hindrance in the alkyl halide. In fact, the E2 reactivity of alkyl halides is tert RX sec RX prim RX, which is opposite to their SN2 reactivity. 

Several useful reactions for the synthesis of alkyl halides that we already have encountered are summarized below with references to the sections that supply more detail  

A summary of these and some other reactions for the synthesis of organohalo-gen compounds is given in Table 14-5 at the end of the chapter (pp. 587-589). 

Exercise 14-2 a. Methyl iodide can be prepared from potassium iodide and dimethyl sulfate. Why is dimethyl sulfate preferable to methanol in reaction with potassium iodide  

Presented below are some of the most frequently used methods of preparing aikyl halides. It is. important to note that some of the reactions permit the incorporation of one halogen into a moiecuJe, while other reactions allow polyhalogenation of a molecule. 

This reaction follows the Markovnikov addition rule which states that the H or (+) portion of the addendum adds to the olcfinic carbon having the most hydrogens. 

This reaction follows anti-Msirkovnikov addition, the H adds to the olcftnic carbon containing the fewest hydrogens. 

This reaction is unique because it permits one to place a bromine atom on a molecule containing an olefin linkage and the product retains the C=C. For this reaction to take place there must always be a H on an a— or allylic carbon (carbon adjacent to OC). This is the H that is replaced by the Br. If there are several a-carbons each containing H, then the Br may go to any of the a-carbons, i.c., 

The number of potential products and the ease with which they can be separated determines the utility of this reaction. 

The solvation of ionic species involved in a reaction has to be considered. Furthermore, many reactions involve metal-ion catalysis in which the principles of hard and soft acids and bases come into play. Thus a large soft metal may facilitate the reaction of the softer iodides, allowing a harder base to react at the carbon centre. Finally, there are radical reactions based on the alkyl halides, particularly bromides and iodides, involving homolytic fission of the C-X bond. 

Many of the convenient methods of preparing alkyl halides are based on the reactions of alcohols with reagents such as thionyl chloride and phosphorus pentachloride. These are dealt with in more detail in Section 2.3 on alcohols. The nucleophilic substitution of an alkyl methanesul-fonate or toluene-4-sulfonate with a sodium or potassium halide is a useful method. 

Another widely used series of reactions involves the addition of the hydrogen halides to alkenes. These are discussed in more detail later in the section on alkenes. Other methods that find some use include the decarboxylation of the dry silver salts of carboxylic acids by the halogens (the Hunsdiecker reaction). 

A number of radical reactions involving substitution at an allyUc position, for example with TV-bromosucdnimide (NBS), are useful synthetic methods. NBS, in the presence of dibenzoyl peroxide as an initiator, reacts more rapidly at a secondary rather than a primary allylic position. 

Many of the reactions of alkyl halides with oxygen nucleophiles represent a balance between nucleophilic substitution and elimination. These reactions may occur together, giving mixtures of products. 

The apparent transfer coefficient, as derived from the peak width and the variation of the peak potential with the scan rate, is small (between 0.2 and 0.3) in all cases. This rules out the occurrence of a stepwise mechanism (46, 47), in which the follow-up, bond-breaking step would have been 

This conclusion falls in line with the fact that the anion radical could neither be detected after collision of the parent halide with alkali metal atoms in the gas phase (Compton et ai, 1978) nor upon y-irradiation in apolar or weakly polar solid matrixes at 77 K by esr spectroscopy (Symons, 1981). However, these observations are not absolute proofs that the anion radicals do not exist they might exist and be too short lived to be detectable. On the other hand, the reaction medium and the driving force conditions are quite different from those in the electrochemical experiments, which rendered necessary an independent investigation of the problem in the latter. 

The experimental kinetic data obtained with the butyl halides in DMF are shown in Fig. 13 in the form of a plot of the activation free energy, AG, against the standard potential of the aromatic anion radicals, Ep/Q. The electrochemical data are displayed in the same diagrams in the form of values of the free energies of activation at the cyclic voltammetry peak potential, E, for a 0.1 V s scan rate. Additional data have been recently obtained by pulse radiolysis for n-butyl iodide in the same solvent (Grim-shaw et al., 1988) that complete nicely the data obtained by indirect electrochemistry. In the latter case, indeed, the upper limit of obtainable rate constants was 10 m s , beyond which the overlap between the mediator wave and the direct reduction wave of n-BuI is too strong for a meaningful measurement to be carried out. This is about the lower limit of measurable 

By refluxing the alcohol with a mixture of concentrated hydrochloric acid and anhydrous zinc chloride, for example  

By the action of thionyl chloride upon the alcohol alone or mixed with pyridine (to absorb the hydrogen chloride formed in the reaction), for example  

The dichlorides of aliphatic glycols are obtained by reaction with thionyl chloride in the presence of a small quantity of pyridine, for example  

The chlorides of secondary aliphatic alcohols are prepared by method 1, for example — 

The chlorides of cycloaliphatic alcohols may be prepared by heating the alcohol with concentrated hydrochloric acid and anhydrous calcium chloride, for example — 

T0747 SteamTech Environmental Services, Inc., and Integrated Water Resources Steam-Enhanced Extraction (SEE) 

T0834 Ultrox International/U.S. Filter, Ultrox Advanced Oxidation Process 

T0894 Xerox Corporation, Two-Phase Extraction System 

T0898 Zapit Technology, Inc., Zapit Processing Unit 

T0130 Bohn Biofilter Corporation, Bohn Off-Gas Treatment 

Substitution parameters A, calculated from a least-squares regression analysis, are collected in Table 4.17. By applying eqs. (4.3)-(4.6), the 13C chemical shifts of halomethanes can be predicted with a standard deviation of about 4 ppm. 

The a carbon shifts of haloalkanes depend on temperature and solvent. Strong solvent effects are observed for the iodinated carbon atoms in iodoalkanes, as shown in Table 4.18 [253]. As expected from theory [254], carbon-13 solvent shifts are linearly dependent on (e — l)/(2e + n2) (e dielectric constant n refractive index) [253]. 

No correlation with substituent properties can be recognized for the fi effect of halogens in Table 3.2. The magnitude of shielding due to the y effect, however, decreases with increasing size of the halogen (Table 3.2). A reduced population of the gauche conformer 

A systematic investigation of chloro-substituted ethanes CH3 XC1X — CH3 yC1y shows that for y = 0, the C-l resonance is shifted to lower field by about 30 ppm per hydrogen-chlorine substitution on C-l with increasing chlorine substitution at C-2 the relative deshielding for C-l decreases [256], 

As the range of chemical shifts is an order of magnitude larger for 1 C than for H, CMR is better suited for investigating stereoisomers. This has been demonstrated by 1- C NMR measurements on 2,4-dichloropentane and 2,3-dichlorobutane, which are models 

Houben-Weyl, Methoden der Organischen Chemie, fol V/ lb, pp 9-44, 134-180 Acct Chem Res 12 198, 430 (1979) 

Alt cat CfcTlCfe LiAlHt, TiCl3 or TiCL, UAIH4, C1O3 cat Co(II)galen, electrolysis B 

Draw structures for these compounds a) 1-Pentyne b) 2,3,4-Trimethyl-5-undecyne 

As might be expected, the physical properties of alkynes are very similar to those of alkenes and alkanes with the same number of carbons. For example, the boiling points of hexane. 1-hexene, and 1-hexyne are 69°C, 63°C, and 71°C. respectively. 

Alkynes are less common in nature than are alkenes. Alkynes are also less important in industry. The largest use of acetylene is as a fuel for the oxyacetylene welding torch, which burns at a very high temperature. 

Click Coached Tutorial Problems to practice Naming Alkanes, Alkenes, and Cycloalkanes or to practice Drawing 

CH2CI2, and C6F5X(—) are calculated from electron affinities, electron impact data, and dissociation energies. 

The electron affinities of chlorinated biphenyls and naphthalenes were estimated from half-wave reduction potentials by assuming that the solution energy differences were constant. Now that it is possible to estimate solution energy differences, more accurate Ea are obtained. The Ea for all the isomers of the chlomaphthalenes are calculated using CURES-EC. 

The negative-ion mass spectra for more than 300 environmental pollutants have been reported at two temperatures 373 K and 523 K. The electron affinities of aromatic hydrocarbons, phthalates, chloroethylenes, chlorobenzenes, chloronphtha-lenes, chlorinated biphenyls, and nitrobenzenes have been measured, but the Ea of others, such as the bromobenzenes and chlorinated dioxins, have not. If we know the Ea of the parent compounds, the electron affinities and bond dissociation energies of these compounds can be estimated and compared with the NIMS data. These values are examined using CURES-EC. 

One use of the electron affinities of molecules is to predict the sensitivity and temperature dependence of the ECD to compounds that might be analyzed. Many environmental pollutants have different multiple substituents. Pesticides are highly chlorinated organic compounds. The chlorinated biphenyls, naphthalenes, and dioxanes are among the most toxic compounds. The temperature dependence of these compounds in the ECD is important, but has not been extensively studied. When the electron affinities and bond dissociation energies are known, the temperature dependence can be calculated from the kinetic model. This is done for the chlorinated biphenyls and naphthalenes, and the calculated temperature dependence is then compared with experiment. These calculations offer clues about the best conditions for analysis. 

The temperature dependence of the alkyl halides was one of the first subjects to be studied using the ECD. These are the simplest to analyze because often there is only one temperature region when dissociative thermal electron attachment is exothermic. This means that the EDEA, the energy of dissociative electron attachment, is positive EDEA = a(X) - D(R —X). The alkyl bromides, iodides, and chlorides are among the few organic compounds that have positive EDEA. Like the homono-nuclear diatomic halogen ions, the ground-state anionic curves for these molecules are M(3), with positive values for all three Herschbach metrics—EDEA, Ea, and VEa. 

The mechanism of the reaction has not been irrefutably established, ft has been found that exchange was not observed over different metals [70,71]. The reaction was considered both as nucleophilic [72,73] or electrophilic [74] attack. Retention of configuration was found on Pd whereas racemization was almost complete on Ni [2,75]. 

CH2F2 over Pd/C [81]. Hydrogenolysis of neopentyl iodide on Pt/MgO catalyst takes place via a nr-complexed half-reaction state [82]. 

Ketones as a group are considered narcotic. The primary hazard of the esters is polymerization. Many of them are flammable liquids and polymers. The DOT does list some ester compounds as Class 6.1 poisons and, again, these compounds have chlorine added, which accounts for their toxicity. For example, ethyl chloroformate is an ester that has an NFPA health designation of 4. Remember that too much of any chemical can be toxic, so too much of an anesthetic or a narcotic can be toxic. 

There are three ways alkyl halides can be named. They are all correct naming conventions, and the compounds may be listed under any one of the possibilities. When researching the compounds in reference books, you may have to look under the alternate names to find information on the compound. The first naming convention is one in which the radical is named first, the ine is dropped from the halogen, and an ide ending is added. For example, if the compound has one carbon, the radical for one carbon is methyl. If there is chlorine attached to the methyl radical. 

If fluorine is attached to a one-carlxtn radical, the name is methyl fluoride, and so on. 

Methyl bromide Bromomethane CHoBr Ethyl fluoride Fluoroethane C2H5F Propyl chloride Chloropropane C3H7CI 

Trichloro methane Methyl trichloride CHCI3 Dibromo methane Methyl dibromide CH2Br2 Tetrachloro methane Methyl tetrachloride Carbon tetrachloride CCI4 

Rate constants vary from 85.4 x 10 s for the 5-chloro-l,10-phenanthroline 

The reaction of Ni(I) complexes with alkyl halides has been examined. The octaethylisobacteriochlorin complex reacts with CH3I to produce the neutral Ni(II) complex, CH4, and p/294) yi(jence is presented for the intermediacy of an alkyl-Ni(III) species. Ni(I)(tetra-N-methylcyclam) reacts with 1,5-dihaloalkanes yielding cyclopentane. Comparison of the data for these reactions suggests a common inner-sphere electron transfer. With other disubstituted alkanes, the reaction leads to the formation of alkenes. No transient organonickel species are observed. The reaction between electrochemically generated [(TPP)Co(I)] (TPP = tetraphenylporphyrin) and 17 different alkyl halides has been monitored by cyclic voltammetry. An Sjy2 reaction mechanism was postulated for all 

Irradiation of a mixture of methane and chlorine results in the formation of different chlorides of methane. It has been observed that for this photoreaction to proceed it is not necessary to irradiate the reaction mixture continuously during the reaction. It is sufficient to irradiate it for only a short time and the reaction then will continue in the dark. Since the irradiation is used only for triggering the reaction this first step is called initiation. As was explained in the previous section this step 

In this reaction a chlorine radical can also react with methyl chloride  

The final product mixture also contains dichloromethane CH2CI2, trichlorometh-ane CHCI3 and tetrachloromethane CCI4. 

Except for the methyl chloride which is gaseous under standard conditions, the chlorides of methane are liquid substances which are used widely in the laboratory, in industry and also in medicine. Trichloromethane, CHCI3, is also known under the traditional name of chloroform and can be used as an anesthetic. Tetrachloromethane or carbon tetrachloride is a very good solvent with practical applications in the laboratory, but it must be handled with care because of its carcinogenic properties. 

The freon molecule possesses two kinds of chemical bonds, C-F and C-Cl which differ markedly in bond energies. While the C-F bond is strong with a bond energy of 485 kJ/mol, the C-Cl bond is much weaker with a bond energy of 331 kJ/mol. Consequently, irradiation of a freon molecule like for instance CF3CI, results in the breaking of the C-Cl bond and yields the following radicals  

Halogenated organic compounds are commonly used as electrophiles in substitution reactions. Although other compounds can also serve as electrophiles, we will focus our attention for now on compounds containing halogens. 

Recall from Section 4.2 that systematic (lUPAC) names of alkanes are assigned using four discrete steps  

Number the parent chain and assign a locant to each substituent. 

The same exact four-step procedure is used to name compounds that contain halogens, and all of the rules discussed in Chapter 4 apply here as well. Halogens are simply treated as substituents and receive the following names fluoro-, chloro-, bromo-, and iodo-. Below are two examples  

As we saw in Chapter 4, the parent is the longest chain, and it should be numbered so that the first substituent receives the lower number  

Triphenylphosphine-carbon tetrachloride converts epoxides into cisA, 2-dichlorides, a process already known to occur with triphenyldichloro-phosphorane. The in situ generation of hydrogen bromide and isobutene is a simple laboratory preparation of t-butyl bromide.  

Scheffold and E. Saladin, Angew. Chem. Internat. Edit., 1972, 11, 229. 

Two reports have described the use of nickel-phosphine complexes as catalysts in the cross-coupling of Grignard reagents with aryl and vinyl halides. The reaction of benzal and other benzylic halides with lithium di-alkylcopper reagents has been explored as a potential route to quaternary carbon atoms preliminary results are not promising.  

In pursuit of a stereoselective synthesis of carbohydrates by telomerization of halogenated vinylene carbonates, Japanese authors have reported that nickel carbonyl in THF reductively converts polyhalogenomethyl groups into di- or mono-halogenomethyl groups under relatively mild conditions. 

No stereochemical integrity is observed in the phosphine-induced de-bromination of 1,2-dibromides, /raw -olefins being uniformly produ d by a mechanism considered to involve an intermediate ion-pair. 

Silver difluorochloroacetate smoothly converts bromo-compounds into the chloro-analogues for example, n-octyl bromide is converted into 

A further method is described for the conversion of allylic alcohols into chlorides without rearrangement methanesulphonyl chloride reacts with allylic alcohols at 0°C in the presence of lithium chloride, DMF, and collidine to give pure, unrearranged allylic chlorides non-allylic alcohols are inert to such conditions. This technique has been used by Meyers in a synthesis of an insect pheromone. 

Reactions.— DMF is recommended as solvent for the sodium borohydride reduction of primary and secondary alkyl halides to the corresponding hydrocarbons this reaction, which proceeds at room temperature, shows the kinetic behaviour of an 5 fj2 process. The intermediacy of organoboranes in the analogous reduction of tertiary halides has been demonstrated  

The direct oxidation of alkyl halides to carbonyl compounds by DMSO occurs in good yield under mild conditions in the presence of silver ion, which assists formation of the alkoxysulphonium intermediate silver perchlorate is the salt of choice, other salts competing nucleophilically with DMSO for the substrate. Oxidation of primary halides stops cleanly at the aldehyde stage, except when an excess of silver salt is present. As has been already described, sodium tetracarbonylferrate converts alkyl bromides into the homologous aldehydes this conversion is most successful with primary halides, n-decanal being obtained in 77% yield from n-nonyl bromide. 

The coupling of Grignard reagents and alkyl halides is dramatically enhanced when the latter possesses proximate functionality capable of com-plexation, and hence of transition-state stabilization whereas neither n-pentyl nor ethoxyethyl bromide react with iodomagnesium phenylacetylide, the bromide (196) does.  

In reactions, chlorosulfonic acid is often employed as a solution in halogenated solvents. It dissolves readily in such solvents, provided that they contain hydrogen, e.g. chloroform, dichloromethane, 1,2-dichloro- or tetrachloroethane. On the other hand, the reagent is only sparingly soluble in halogenated solvents without hydrogen, e.g. carbon tetrachloride or tetrachloroethene. 

With hexachlorocyclopentadiene, the initially formed chlorosulfonate ester may react further to give undecacyclopentacyclodecyl chlorosulfonate, as described in Section 1, p 150. 

The reaction with chlorosulfonic acid has been successfully extended to the telomer iodides 41, which, by heating with excess chlorosulfonic acid yield the corresponding chlorosulfonates 42 (Equation 18).  

It has been discovered that chlorosulfonic acid is much more reactive towards substrates containing a CH2CF2I group, as compared with the analogous perfluorinated compounds, and these reactions often proceed at low temperatures as illustrated by the conversion of compound 43—f44 (Equation 19). 

The fluorocarbon chlorosulfonates represent a new class of compound and are useful intermediates in the synthesis of fluorocarbon carboxylic acids and derivatives.  

The stoichiometry and kinetics of the reactions of [Co(dmgH)2L] and polyhalomethanes (RX) in acetone and benzene are in accord with a two-step mechanism  

The existence and reactivity of the free-radical intermediate for the case R = CCI3 were examined by kinetic competition with 4-hydroxy-2,2,6,6-tetramethyl-piperidinyloxy (4-htmpo). Numerical integration techniques yielded an estimate of the relative rate constants for the reaction of CCl3 with 4-htmpo (kHTMPo) vs. kco in benzene, kHXMPo/ o = 1.8 0.1 (25°C). 

Hydrogen-saturated alkaline solutions of cyanocobaltate with the CN Co ratio of 5 1 react with aryl halides to produce o--arylpenta-cyanocobaltates(III). Hydrogenolysis and cyanation products were also observed. The reactive species is most likely [Co(CN)4], since no organocobaltates were formed at CN Co ratios 5 1. 

The rapid reaction of LiMe2Cu with trityl halides in ether produces trityl radicals, as shown by ESR. The reaction with a cyclizable alkyl halide, 6-iodo-l-heptene, produced the cyclic coupled product. Both results are strongly indicative of the intermediate radical formation by a singleelectron transfer pathway. 

Cobaloximes(I) and hydridocobaloximes can be arylated with aryl halides with electron-withdrawing substituents, consistent with both electron transfer and Sn2 displacement mechanisms. 

In this example, protection at the primary alcohol was used temporarily to allow acetal protection at the secondary alcohol. The silyl protecting group was then removed selectively to free the alcohol using tetrabutylammo-nium fluoride in THF (Eq. 6.45), taking advantage of the high affinity of fluoride for silicon. Other reagents include dilute HF or acetic acid [22]. 

Chlorine or bromine may be incorporated by substitution for hydrogen under free radical conditions. This is useful when the substrate is a highly symmetric compound or contains a site especially prone to free-radical formation. Otherwise complex mixtures of isomers are obtained. 

Anhydrous hydrogen chloride, bromide, or iodide will add to alkenes by a carbocationic mechanism to give Markovnikov products. The products may have rearranged structures if the first intermediate carbocation can improve in stability by a 1,2-hydride or alkyl shift. Addition to a, -unsaturated carbonyl compounds affords the -halo compounds (Eq. 6.46) [74], which are prone to elimination and thus often isolated as the acetals. Aqueous 

---

N,N,N, N -tetramethyl-l,8,-naph-thalenediamiDe M.P. 51 C. A remarkably strong mono-acidic base (pKg 12-3) which is almost completely non-nucleophilic and valuable for promoting organic elimination reactions (e.g. of alkyl halides to alkenes) without substitution. 

These reactions follow first-order kinetics and proceed with racemisalion if the reaction site is an optically active centre. For alkyl halides nucleophilic substitution proceeds easily primary halides favour Sn2 mechanisms and tertiary halides favour S 1 mechanisms. Aryl halides undergo nucleophilic substitution with difficulty and sometimes involve aryne intermediates. 

NaOCHjCHa. White solid (Na in EtOH). Decomposed by water, gives ethers with alkyl halides reacts with esters. Used in organic syntheses particularly as a base to remove protons adjacent to carbonyl or sulphonyl groups to give resonance-stabilized anions. 

Williamson ether synthesis Alkyl halides react with sodium or potassium alkoxides or phenox-ides to give ethers. 

Although the yields are often poor, especially for halides other than primary alkyl halides, it remains a valuable method for synthesizing unsymmetrical ethers. 

Wuftz synthesis Alkyl halides react with sodium in dry ethereal solution to give hydrocarbons. If equimolecular amounts of two different halides are used, then a mixture of three hydrocarbons of the types R — R, R — R and R —R, where R and R represent the original radicals, will be formed. The yields are often poor owing to subsidiary reactions taking place. 

Sheppard N and De La Cruz C 1998 Vibrational spectra of hydrocarbons adsorbed on metals. Part II. Adsorbed acyclic alkynes and alkanes, cyclic hydrocarbons including aromatics and surface hydrocarbon groups derived from the decomposition of alkyl halides, etc Adv. Catal. 42 181-313... 

A wide class of aiyl-based quaternary surfactants derives from heterocycles such as pyridine and quinoline. The Aralkyl pyridinium halides are easily synthesized from alkyl halides, and the paraquat family, based upon the 4, 4 -bipyridine species, provides many interesting surface active species widely studied in electron donor-acceptor processes. Cationic surfactants are not particularly useful as cleansing agents, but they play a widespread role as charge control (antistatic) agents in detergency and in many coating and thin film related products. 

This zinc-copper couple reacts with methanol, the mixture reducing an alkyl halide to an alkane ... 

At ordinary temperatures, zinc forms an addition compound with an alkyl halide (cf magnesium) ... 

By the action of alkyl halides on the silver salt of the acid. 

The Alkyl Halides. Ethyl bromide and iodide (see below) are typical alkyl halides. Compounds of this class are of very great importance in synthetic work, owing to the reactivity of the halogen atom. This is illustrated by the following reactions ... 

The alkyl halides are also of great importance in synthetic operations (e.g.) using Grigard reagents (p. 280). acetoacetic ester (p. 269) and malonic ester (p. 2- S)-... 

By the action of potassium cyanide on the corresponding alkyl halide. 

Thiourea, unlike urea, readily reacts in the tautomeric form (I) in the presence of suitable reagents, particularly alkyl halides thus benzyl chloride reacts with... 

The preparation of pure primary amines by the interaction of alkyl halides and ammonia is very difficult, because the primary amine which is formed reacts with unchanged alkyl halide to give the secondary amine the latter... 

This direct sulphonation should be compared with the indirect methods for the preparation of aliphatic sulphonic acids, e.g., oxidation of a thiol (RSH -> RSOjH), and interaction of an alkyl halide with sodium sulphite to give the sodium sulphonate (RBr + Na,SO, -> RSO,Na + NaBr). 

When the sodium derivative, which is used in ethanol it solution without intermediate isolation, is boiled with an alkyl halide, e.g., methyl iodide,... 

Substitution Derivatives of Ethyl Malonate, Ethyl malonate resembles ethyl acetoacetate in that it gives rise to mono- and di-substituted derivatives in precisely similar circumstances. Thus when ethanolic solutions of ethyl malonate and of sodium ethoxide are mixed, the sodium derivative (A) of the enol form is produced in solution. On boiling this solution with an alkyl halide, e.g, methyl iodide, the methyl derivative (B) of the keto form is obtained. When this is treated again in ethanolic solution with sodium ethoxide, the... 

The Friedel-Crafts Reaction, in which an aromatic hydrocarbon reacts with an alkyl halide under the influence of aluminium chloride ... 

The preparation of acetophenone (p. 255) is a modification of this method, the alkyl halide being replaced by an acid chloride, with the consequent formation of a ketone. 

The Fittig Reaction, in which sodium reacts with a mixture of an aryl and an alkyl halide, forming the sodium halide and the corresponding hydrocarbon ... 

When an alkyl halide is heated with a trialkyl phosphite, an ester of a phos-phonic acid is produced. This is known as the Arbusov Reaction ... 

Methyl iodide ethyl bromide ethyl iodide, higher alkyl halides, chloroform, iodoform, carbon tetrachloride, chlorobenzene, bromobenzene, iodobenzene, benzyl chloride (and nuclear substituted derivatives)... 

Alkyl and aryl-alkyl halides form 2-naphthyl ethers with 2-naphthol. 

Formation of 2 naphthyl ethers. Alkyl halides and aryl-alkyl halides (e.g. benzyl chloride) are converted into 2-naphthyl ethers thus ... 

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