Rapidity of Reaction

2) An explosive is a chemical substance or a mixture of chemical substances, which when subjected to heat, percussion, detonation or catalysis, undergoes 

An explosive is a substance or device which produces, upon release of its potential energy, a sudden outburst of gases thereby exerting high pressure on its surroundings. 

Thus there are two important aspects of a chemical reaction which results in an explosion. 

Rapidity of reaction distinguishes an explosive reaction from an ordinary combustion reaction and therefore, an explosive reaction takes place with great speed. Unless the reaction occurs rapidly, thermally expanded gases are dissipated in the medium slowly, so that no explosion results. Again an example of wood or coal fire makes it clear. When a piece of wood or coal bums, there is an evolution of heat and formation of gases, but neither is liberated rapidly enough to cause an explosion. 

This means that the fundamental features possessed by an explosive are  

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A remarkable feature of the Birch reduction of estradiol 3-methyl ether derivatives, as well as of other metal-ammonia reductions, is the extreme rapidity of reaction. Sodium and -butyl alcohol, a metal-alcohol combination having a comparatively slow rate of reduction, effects the reduction of estradiol 3-methyl ether to the extent of 96% in 5 minutes at —33° lithium also effects complete reduction under the same conditions as is to be expected. Shorter reaction times were not studied. At —70°, reduction with sodium occurs to the extent of 56 % in 5 minutes, although reduction with lithium is virtually complete (96%) in the same time. (The slow rates of reduction of compounds of the 5-methoxytetralin type is exemplified by 5-methoxy-tetralin itself with sodium and f-butyl alcohol reduction occurs to the extent of only 50% in 6 hours vs. 99+% with lithium.) The iron catalyzed reaction of sodium with alcohols must be very fast since it competes so well with the rapid Birch reduction. One cannot compensate for the presence of iron in a Birch reduction mixture containing sodium by adding additional metal to extend the reaction time. The iron catalyzed sodium-alcohol reaction is sufficiently rapid that the aromatic steroid still remains largely unreduced. 

Rapidity of reaction with water varies among these chemicals from slow to explosively violent. Reaction with water may generate toxic, corrosive or flammable gaseous reaction products or generate sufficient heat or off-gas to rupture unrelieved containment. 

Gedroiz, K. K. (1914). Colloidal chemistry as related to soil science. II. Rapidity of reaction exchange in the soil, colloidal condition of the soil saturated with various bases and the indicator method of determining the colloidal content of the soil. Zh. Opytn. Agron. 15, 181-208. 

Free boroles are highly reactive four t-electron antiaromatic systems, and only a few sterically protected derivatives have been isolated up to 1995. The only known isolable monomeric boroles without annulated aromatic groups are derivatives of 1,2,3,4,5-pentaphenylborole (1), first described in 1961. The antiaromaticity is evident by the rapidity of reactions that remove the empty 2p -orbital on boron from conjugation (Lewis complexation) or disrupt the borole ring system altogether (e.g., Diels-Alder addition). An earlier review in the first edition of Comprehensive Heterocyclic Chemistry (CHEC-I) has only dealt with the borole ring <84CHEC-I(1)629>. 

The empty 2/j,-orbital on boron interacting with the ji-electrons of the butadienylidene system in borole (5) is proved by the pronounced bathochromic shift in the visible spectrum compared with that of its pyridine adduct. This Ti-electron delocalization in boroles is destabilizing and produces a 471-electron antiaromatic system. The antiaromaticity is further evidenced by the rapidity of reactions that remove the 2p ,-orbital on boron from conjugation. These reactions include Lewis complexation, transition metal complexation, or borole ring opening reactions such as Diels-Alder addition, oxidation, and protodeboration. This removal of the antiaromaticity from borole results in transforming the compound to a typical, low reacting, sterically hindered arylborane. 

The rapidity of reaction is not unexpected since the reaction is believed to be occurring through simple addition of the uranyl ion to the carboxylate sites on PANa and the reaction may actually occur in a millisecond or shorter time frame. 

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