Acid chlorides, relative reactivity toward

The relative reactivities toward nucleophilic addition-elimination are acyl chlorides > acid anhydrides > esters carboxylic acids > amides > carboxylate ions. Hydrolysis, alcoholysis, and aminolysis are reactions in which water, alcohols, and amines, respectively, convert one compound into two compounds. 

Figure 16 Relative reactivities of two diarylmethyl chlorides toward 2-methyl-1-pentene in CH2O2 at -70° C as a function of the Lewis acid concentration. (From Ref. 183, reprinted by permission of Kluwer Academic Publishers.)...

Relative reactivities of carboxylic acid derivatives toward nucleophilic acyl substitution. A more reactive derivative may be converted to a less reactive derivative by treatment with an appropriate reagent. Treatment of a carboxylic acid with thionyl chloride converts the carboxylic acid to the more reactive acid chloride. Carboxylic acids are about as reactive as esters under acidic conditions, but are converted to the unreactive carboxylate anions under basic conditions. 

Figure 3 Relative Reactivity of two Diarylmethyl Chlorides towards 2-Methyl-1-pentene in CH2CI2 at -70 °C as a Function of the Lewis Acid Concentration. ...

As mentioned before, all acyl compounds participate in the addition-elimination process. Acid chlorides are especially reactive toward nucleophiles. Their carbonyl groups, being the least stabilized by resonance, have the highest energy and are the most reactive. So, an initial addition reaction with a nucleophile is relatively easy. The chloride atom of acid chlorides is an excellent leaving group, and sits poised, ready to depart once the tetrahedral intermediate has been formed... 

When maltose was treated with 8 molar equivalents of benzoyl chloride in pyridine at —40°, it afforded octa-0-benzoyl-/3-maltose, l,2,6,2, 3, 4, 6 -hepta-0-benzoyl-/3-maltose, and l,2,6,2, 3, 6 -hexa-0-benzoyl-/3-maltose in yields of 3, 79, and 12%, respectively.69 Similar treatment of methyl /3-maltoside with 7 molar proportions of benzoyl chloride in pyridine gave crystalline methyl 2,6,2, 3, 4, 6 -hexa-0-benzoyl -/3 - maltoside and methyl 2,6,2, 3, 6 -penta-O -benzoyl -/3 -maltoside in yields of 71 and 23%, respectively.69 Analysis of the relative yields of the products of these reactions suggests that, after HO-3, the 4 -hydroxyl group in maltose and methyl /3-maltoside is the most hindered. Benzoylation of methyl 4, 6 -0-benzylidene-/3-maltoside with 10 molar proportions of reagent gave 2,6,2, 3 -tetra-0-benzoyl-4, 6 -0-benzylidene-/3-maltoside (71%) and an equimolar mixture (22%) of the 2,6,2 - and 2,6,3 -tribenzoates. These results indicated that the order of reactivity of the hydroxyl groups towards acid halides in pyridine is HO-2, HO-6 > HO-2 HO-3 > HO-3. 

The free radical arylation of thiazole (391) has been performed either by the Gomberg-Bachmann (392) decomposition of aryldiazonium chlorides (119,393), by the thermal decomposition of benzoyl peroxide (394-397) or N-nitrosoacetanilide (398), or by the photolysis of benzoyl peroxide or iodobenzene (398). The three monophenylthiazoles are obtained in the practically constant proportions 2-phenyl, 60% 5-phenyl, 30% 4-phenyl, 10%, giving the order, 2>5>4, of decreasing reactivity of the three positions of thiazole toward phenyl radicals (398). Competition reactions with nitrobenzene (397) gave an estimation of the globed reactivity of thiazole relative to benzene of 0.75 with the partial rate factors f2 = 2.2, /s=1.9, /4 = 0.5. When the thermolysis of benzoyl peroxide is performed in acetic acid solution, the substrate in reaction is the conjugate acid of thiazole the global reactivity is enhanced to 1.25,... 

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