Kinetics nucleophilic aliphatic substitution

Kinetics of the transformations of the N-F class of fluorinating agents in water, acetonitrile, alcohols, and aqueous solutions of alkali metal hydroxides have been studied.159 Other kinetic studies include die reactions of triphenylphosphine with 3-methoxy- or 3-acctoxy-4,4,5,5-tetrasubstitutcd-1,2-dioxolanes,160 the reactions of 2-amino-5-chlorobenzophenone witii HC1 in MeOH-H20 (die aspect of nucleophilic aliphatic substitution lies in certain products arising from attack of AH2 on CH3OH there are six products in all, and rate constants are evaluated for die formation of each of them),161 and the hydrolysis of derivatives of diazidophenyhnethane.162... 

Just because this reaction is simiiar to the previous nucleophilic aliphatic substitution, one should not jump to the conclusion that the rate law and kinetics wilt be similar. The rate Uzw is determined from experimental obsen/atiam It relates the rate of reaction at a particular point to the species concentrations at that same point. In this case if one consults an organic chemistry text, one will find that the rate law is... 

The field of chemistry that deals with rates of reaction, and in particular with dependence of rates on concentration, is called kinetics. Let us see what kinetics can tell us about nucleophilic aliphatic substitution. 

As is the case with nucleophilic aliphatic substitution, nucleophilic aromatic substitution (SNAr) can occur by processes that exhibit either first- or second-order kinetics. In contrast to the aliphatic reactions, however, the first-and second-order aromatic reactions are quite different in character. 

The following studies, some involving kinetics, are also of interest for nucleophilic aliphatic substitution. 

Other terms that he invented include the system of classification for mechanisms of aromatic and aliphatic substitution and elimination reactions, designated SN1, SN2, El, and E2. "S" and "E" refer to substitution and elimination, respectively, "N" to nucleophilic, and "1" and "2" to "molecularity," or the number of molecules involved in a reaction step (not kinetic order, having to do with the equation for reaction rate and the concentration of reactants). Ingold first introduced some of these ideas in 1928 in a... 

Most of the kinetic measures of solvent effects have been developed for the study of nucleophilic substitution (Sn) at saturated carbon, solvolytic reactions in particular. It may, therefore, be helpful to give a brief review of aliphatic nucleophilic substitution. Two mechanistic routes have been clearly identified. One of these is shown by... 

Neglecting solvent effects is extremely hazardous. Equilibria and kinetics can be dramatically altered by the nature of the solvent For example, the rate of nucleophilic substitution reactions spans 20 orders of magnitude in going from the gas phase to polar and nonpolar solvents. A classical example of a dramatic solvent effect on equilibrium is the tautomerism between 1 and 2. In the gas phase, the equilibrium lies far to the left, while in the solution phase, 2 dominates because of its much larger dipole moment." Another classical example is that the trend in gas-phase acidity of aliphatic alcohols is reverse of the well-known trend in the solution phase in other words, in the solution phase, the relative acidity trend is R3COH < R2CHOH < RCH2OH, but the opposite is true in the gas phase. ... 

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