Alkyl halides comparison

Comparison of SnI and Sn2 Mechanisms of Nucleophilic Substitution in Alkyl Halides... 

Triflates of aluminum, gallium and boron, which are readily available by the reaction of the corresponding chlorides with triflic acid, are effective Fnedel-Crafis catalysis for alkylation and acylation of aromatic compounds [119, 120] Thus alkylation of toluene with various alkyl halides m the presence of these catalysts proceeds rapidly at room temperature 111 methylene chloride or ni-tromethane Favorable properties of the triflates in comparison with the correspond mg fluorides or chlorides are considerably decreased volatility and higher catalytic activity [120]... 

Rate constants and products have been reported for solvolysis of benzhydryl chloride and /7-methoxybenzyl chloride in 2,2,2-trifluoroethanol (TFE)-water and-ethanol, along with additional kinetic data for solvolysis of r-butyl and other alkyl halides in 97% TFE and 97% hexafluoropropan-2-ol. The results are discussed in terms of solvent ionizing power Y and nucleophilicity N, and contributions from other solvation effects are considered. Comparisons with other 3 nI reactions show that the solvolyses of benzhydryl chloride in TFE mixtures are unexpectedly fast an additional solvation effect influences solvolysis leading to delocalized cations. 

Fig. 10.1 Comparison of boiUng points of some alkyl halides...

Comparison of the configuration of the stannane with the prodncts of reaction reveals that primary alkyl halides that are not benzyhc or a to a carbonyl react with inversion at the lithium-bearing carbon atom. In the piperidine series, the best data are for the 3-phenylpropyl compound, which was shown to be >99 1 er. In the pyrrolidine series, the er of the analogous compound indicates 21-22% retention and 78-79% inversion of configuration. Activated alkyl halides such as benzyl bromide and teri-butyl bromoacetate afford racemic adducts. In both the pyrrolidine and piperidine series, most carbonyl electrophiles (i.e. carbon dioxide, dimethyl carbonate, methyl chloroformate, pivaloyl chloride, cyclohexanone, acetone and benzaldehyde) react with virtually complete retention of configuration at the lithium-bearing carbon atom. The only exceptions are benzophenone, which affords racemic adduct, and pivaloyl chloride, which shows some inversion. The inversion observed with pivaloyl chloride may be due to partial racemization of the ketone product during work-up. 

A simple diagram depicting the differences between these two complementary theories is shown in Fig. 1, which represents reactions at zero driving force. Thus, the activation energy corresponds to the intrinsic barrier. Marcus theory assumes a harmonic potential for reactants and products and, in its simplest form, assumes that the reactant and product surfaces have the same curvature (Fig. la). In his derivation of the dissociative ET theory, Saveant assumed that the reactants should be described by a Morse potential and that the products should simply be the dissociative part of this potential (Fig. Ib). Some concerns about the latter condition have been raised. " On the other hand, comparison of experimental data pertaining to alkyl halides and peroxides (Section 3) with equations (7) and (8) seems to indicate that the simple model proposed by Saveant for the nuclear factor of the ET rate constant expression satisfactorily describes concerted dissociative reductions in the condensed phase. A similar treatment was used by Wentworth and coworkers to describe dissociative electron attachment to aromatic and alkyl halides in the gas phase. ... 

A rel = 1.2 x 10 6) (Ingold, 1957). Neopentyl halides are known in fact to be extremely stable towards nucleophilic displacement. There are few examples in the gas phase that allow for a full comparison since alkyl halides with P-hydrogens may be prone to undergo elimination reactions simultaneously with displacement. For example, the reaction of F with C2H5C1 proceeds with a rate constant krel = 0.86, compared to that of CH3C1 (Jose, 1976), whereas (CH3)3CCH2C1 reacts with k[cl = 0.61 (Olmstead and Brauman,... 

Swain, C. G., and C. B. Scott, Quantitative correlation of relative rates. Comparison of hydroxide ion with other nucleophilic reagents toward alkyl halides, esters, epoxides, and acyl halides , J. Am. Chem. Soc., 75, 141-147 (1953). 

COMPARISON OF THE HYDROLYSIS OF /-ALKYL FLUOROACETATES WITH THE SOLVOLYSIS OF /-ALKYL HALIDES AT 25°C... 

Reaction of alkyl halides with anions in solution, RX(aq) + Y-(aq), - a steady state treatment and comparison with a pre-equilibrium treatment, 202-204, 360-363... 

Comparison of the second-rate order constants for reactions of the molybdenum and tungsten analogs with a given alkyl halide shows that the tungsten complex reacts six times faster than the molybdenum counterpart (Section VI,E,2). 

Identification of naturally occurring organic sulfur compounds (OSC) is possible by co-chromatography (on capillary GC) and comparison of mass spectra (by GC-MS) with synthesized standards. Methods of preparation of various thiophenes (e.g. from suitable thiophene precursors and coupling with either the appropriate carboxylic acid, aldehyde or alkyl halide) will be outlined in addition to some of their spectral properties (NMR, IR,... 

The ultrasonic field considerably accelerates processes and increases yields of Al-organic complexes with low-active alkyl halides, complexes of sodium, naphthaline, benzoquinoline, and other aromatic compounds [742], Use of US treatment in Ulmann condensation [742] in the presence of copper powder (3.285) allows acceleration of the reaction rate 50 times and a yield of 81% in comparison with <1.5% without US ... 

The nature of alkyl halide and the environment of the phosphorus atom make a substantial contribution to the direction of the reaction. Thus, cyclic phosphites [108], like trialkyl phosphites [110], react with preservation of the coordination of the P(III) phosphorus atom (126-132 ppm). If the alkoxyl group is substituted by amide, alkyl, or aryl, the nucleophilicity of the phosphorus atom in the corresponding amidophosphite (phosphonite) increases in comparison with the trialkyl phosphite. This probably promotes attack by 1 -haloalkyl-2-pyrrolidone at the phosphorus atom and not the oxygen, and this was confirmed experimentally. As a result of the investigated reactions amidophosphonates or ethyl phenyl phosphinates llOa-c were isolated compounds with P(III) were not detected in these cases. 

Sulfides are nucleophiles even when not deprotonated—the sulfur atom will attack alkyl halides to form sulfonium salts. This may look strange in comparison with ethers, but it is, of course, a familiar pattern of reactivity for amines, and you have seen phosphonium salts formed in a similar way (Chapters 14 and 31). 

A comparison of E2 elimination reactions using alkyl halides and amines... 

The difference between the chemical behaviour of the substitution products of benzene and the corresponding aliphatic derivatives are well known and are reflected in the values of their dipole momcnxs [Table XCVI), In chlorobenzene, in addition to the bond resonance structures, I and //, there are three additional structures ///, IV and V contributing to the molecular resonance and the dipole moment is lowered in comparison with the alkyl halides. 

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