Tosic acid TsOH

The important point is that, at any one particular temperature, the equilibrium constant is just that—constant. This gives us a means of forcing the equilibrium to favour the products (or reactants) since the ratio of the two must remain constant. Therefore, if we increase the concentration of the reactants (or even that of just one of the reactants), more products must be produced to keep the equilibrium constant. One way to make esters in the laboratory is to use a large excess of the alcohol and remove water continually from the system as it is formed, for example by distilling it out. This means that in the equilibrium mixture there is a tiny quantity of water, lots of the ester, lots of the alcohol, and very little of the carboxylic acid in other words, we have converted the carboxylic acid into the ester. We must still use an acid catalyst, but the acid must be anhydrous since we do not want any water present—commonly used acids are toluene sulfonic acid (tosic acid, TsOH), concentrated sulfuric acid (H2SO4), or gaseous HC1. The acid catalyst does not alter the position of the equilibrium it simply speeds up the rate of the reaction, allowing equilibrium to be reached more quickly. 

Direct sulfonation of toluene with concentrated sulfuric acid gives a mixture of ortho and para sulfonic acids from which about 40% of toluene para sulfonic acid can be isolated as the sodium salt. The free acid is important as a convenient solid acid, useful when a strong acid is needed to catalyse a reaction. Being much more easily handled than oily and corrosive sulfuric acid or syrupy phosphoric acid, it is useful for acetal formation (Chapter 14) and eliminations by the El mechanism on alcohols (Chapter 19). It is usually called tosic acid, TsOH, or PTSA (paratoluene sulfonic acid). 

A new interesting concept to further increase the sensitivity of chemical amplification resists has been proposed primarily for 193 nm lithography. An acid amplifier in resist film, inert to radiation, produces a large number of acid molecules by its catalytic reaction with a photochemically generated acid (Fig. 10) [93,94]. In many cases only weak sulfonic acids such asp-toluenesul-fonic acid (tosic acid, TsOH) are generated by this mechanism and an aromatic structure incorporated into acid amplifiers to promote acid cleavage increases 193 nm absorption. 

Recall from Section 9.13 that CH3C6H4SO2- is called a tosyl group, abbreviated by the letters Ts. For this reason, p-toluenesulfonic acid (also called tosic acid) is abbreviated as TsOH. 

Glyme 1,2-Dimethoxyethane TsOH Tosic acid, p-CH,C,H[Pg.4]

Esterification. The preparation of y-chloropropyl acetate was accomplished by heating the components in benzene with a little tosic acid under a Vigreaux column CHjCOjH + HOCH2CH2CH2CI + TsOH HjO + C Ht ---------------CHjCOjCHjCHjCHjCl... 

Such an acid is 4-methylbenzenesulfonic acid (51 commonly known as p-tol-uenesulfonic acid, tosic acid, or p-TsOH this benzene nomenclature system is discussed in Chapter 21, Section 21.2). Another commercially available sulfonic acid is methanesulfonic acid (52), commonly abbreviated as MsOH, where Ms = mesyl. Tosic acid is a crystalline sohd that is cheap, readily available, and soluble in most organic solvents. Throughout most of this book, the acid catalyst is simply referred to as H+, but the actual acid is usually sulfuric acid or tosic acid. 

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