Nitration rate

Substituent Complexest with Chlorina- ation rates Nitration rates ... 

As in the case of MNT, agitation is important in increasing the MNT to DNT nitration rate. Orlova s data for the nitration of p-nitrotoluene with 4/74/23% nitric acid/sulfuric acid/water at 70° are shown in Fig 8... 

As implied in the preceding discussion, deliberate introduction of water into the nitration medium should make step (8) competitive with step (16) even for a reactive XH, and the overall nitration rate changes from zero-order to first order. These phenomena have been observed (Refs 49 49a). Under nearly identical conditions (2.5M HN03, 1.09M H20, ca 0.02M XH in NM soln at 25°), the measured first-order rate constants are 2.5xl0 4, 2.0xl0 4, 1.2xlQ s sec 1 respectively for MeOH, toluene, and n-methyl-2,4,6-triiutroaniiine. Combined with some earlier data, the reactivities"... 

Since mixing of glycol and MA was very thorough and rapid this AT mirrors the progress of the exothermic nitration reaction. Note the strong influence of mixed acid water content on the nitration rate. This agrees with Oehman et al (Ref 56a), except that Roth et al observed... 

DEPENDENCE OF ANILINIUM ION NITRATION RATE AT 25 °C ON HjS04 CONCENTRA... 

OS 32] ]R 16a] ]P 23]Toluene nitration rates determined in the capillary-flow reactor were generally higher than benzene nitration rates [31, 97]. This is not surprising, as it stems from the higher reactivity of toluene towards electrophilic substitution owing to its more electron-rich aromatic core. For instance, at a reaction temperature of 60 °C, rates of 6 and 2 min were found for toluene and benzene nitration, respectively. However, care has to be taken when quantitatively comparing these results, since experimental details and tube diameters vary to a certain extent or are not even listed completely. 

Further, if the rate-determining step involves single-electron transfer, isotope effects should not affect the nitration rate, that is, k lk should be 1. Using ion-cyclotron resonance for studying aromatic nitration in the gas phase, Dunbar et al. (1972) found no isotope effect. 

When nitrating to a nitrogen content of 12% and more the nitration rate is higher, hence no significant divergence exists between nitration on the industrial scale and laboratory experiments. 

Taking into consideration the factor of diffusion Sakurada expresses the nitration rate of cellulose by the equation... 

The activation barrier for such a direct collapse of the ion-radical pair is substantially less than AGet (see pathway Pi in Chart 7) and leads to very fast nitration rates [73]. (The latter underscores the caveat that the viability of ET mechanisms cannot be pre-judged [67] solely by the value of A Get). 

Bennett s explanation of the existence of a maximum in the nitration rate at the sulphuric acid concentration mentioned above is as follows. Since in nitration... 

Thus, the nitration rate would depend on two factors on attaching the nitronium... 

From these results and later experiments (Ingold and co-workers [36,37, 39]) on the influence of solvents on the nitration rate Ingold came to the conclusion that splitting off the proton in the nitration of aromatics does not effect the reaction kinetics. This conclusion differed from that of Bennett and his co-workers [87]. 

In 1948, Titov [35] also studied the problem of the existence of a maximum in the nitration rate at certain concentration of sulphuric acid. He assumed, like Hetherington and Masson, (see p. 33), that cations might be formed in nitration by the attachment of protons to nitro compounds, for exMnple ... 

It is only the first factor in the right side of the equation which affects the nitration rate, since the second factor is very small because of the low rate of nitration of... 

An increase in sulphuric acid concentration results in increase in the concentration of the C6H5N02H+ cation, hence in a decrease in the C6H5N02 concentration which in turn brings about a decrease in the nitration rate. On the other hand the concentration of the N02+ ion increases with increase in sulphuric acid concentration. 

Ingold and his co-workers [36,37,39] inferred from the results of their studies that the nitration rate, VS/ in the presence of sulphuric acid might be expressed roughly by the equation ... 

Consequently, mixing during nitration strongly affects the nitration result vigorous stirring increases the nitration rate. This will be dealt with on pp. 266 and 314. 

The extension of the interfacial area by emulsification explains Miyagawa s [95] observation that the nitration rate can be considerably increased by the action of ultrasonics on a reacting system. For example, nitration of m- xylene to trinitro-m- xylene, which generally takes 2 hr, takes only 30 min when ultrasonics are used. There is no evidence as yet whether and how ultrasonic waves effect group orientations. 

It has also been found that for my nitric acid concentration, the nitration rate is nearly proportional to the molar excess of sulphuric acid as related to the water content of the nitrating mixture. The nitrating acid excess is a factor of special importance in esterification of alcohols ( O-nitration ),... 

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