Initiation by heat

Acrylonitrile will polymerize violendy in the absence of oxygen if initiated by heat, light, pressure, peroxide, or strong acids and bases. It is unstable in the presence of bromine, ammonia, amines, and copper or copper alloys. Neat acrylonitrile is generally stabilized against polymerization with trace levels of hydroquinone monomethyl ether and water. 

The reaction with fluorine occurs spontaneously and explosively, even in the dark at low temperatures. This hydrogen—fluorine reaction is of interest in rocket propellant systems (99—102) (see Explosives and propellants, propellants). The reactions with chlorine and bromine are radical-chain reactions initiated by heat or radiation (103—105). The hydrogen-iodine reaction can be carried out thermally or catalyticaHy (106). 

An expanding development is the use of peroxodisulfates as oxidants in organic chemistry (80,81). These reactions are initiated by heat, light, gamma rays, or transition-metal ions. The primary oxidising species is usually the sulfate ion radical, P hskip -3pt peroxodisulfate anion... 

The most common reaction of methylene chloride is its reaction with chlorine to give chloroform and carbon tetrachloride. This occurs by a free-radical process initiated by heat or light in the gas or Hquid phase. Catalytic chlorination to these same products is also known (see Chlorocarbons and Cm OROHYDROCARBONS, Cm OROFORM). 

Hydrochloric acid may conveniently be prepared by combustion of hydrogen with chlorine. In a typical process dry hydrogen chloride is passed into a vapour blender to be mixed with an equimolar proportion of dry acetylene. The presence of chlorine may cause an explosion and thus a device is used to detect any sudden rise in temperature. In such circumstances the hydrogen chloride is automatically diverted to the atmosphere. The mixture of gases is then led to a multi-tubular reactor, each tube of which is packed with a mercuric chloride catalyst on an activated carbon support. The reaction is initiated by heat but once it has started cooling has to be applied to control the highly exothermic reaction at about 90-100°C. In addition to the main reaction the side reactions shown in Figure 12.6 may occur. 

Functionalization in the 3-position has been accomplished by a Mannich type condensation as shown in Eq. (3.53). The process is initiated by heating binaphthol with N-( -butoxymethyl)morpholine for five days at 150° °. Under these conditions, a mix-... 

Many inorganic compounds and all organic compounds also react directly with O2 under appropriate conditions. Reaction may be spontaneous, or may require initiation by heat, light, electric discharge, chemisorption or various catalytic means. Oxygen is normally considered to be divalent, though the oxidation state can vary widely and includes the values of - -i, 0, —j, —j, —I and —2 in isolable compounds of such species as 02", O3, 03 , 02 , 02 and respectively. The coor-... 

Resistance of a polymer to chemical attack resulting in breakdown of some covalent bonds and formation of new ones. This could involve breakdown initiated by heat and radiation including u.v. light. 

Safety. Since organic peroxides can be initiated by heat, mechanical shock, friction or contamination, an enormous problem in safety presents itself. Numerous examples of this problem have already been shown in this article. Additional examples include the foilowing methyl and ethyl hydroperoxides expld violently on heating or jarring, and their Ba salts also are extremely expl the alkylidene peroxides derived from low mw aldehydes and ketones are very sensitive and expld with considerable force polymeric peroxides of dimethyl ketene, -K>-0-C(CH3)2C(0)j-n, expld in the dry state by rubbing even at —80° peroxy acids, especially those of low mw, and diacetyl, dimethyl, dipropkmyl and methyl ethyl peroxides, when pure, must be handled only in small amts and... 

Aldehydes, both aliphatic and aromatic, can be decarbonylated by heating with chlorotris(triphenylphosphine)rhodium or other catalysts such as palladium. The compound RhCl(Ph3P)3 is often called Wilkinson s catalyst.In an older reaction, aliphatic (but not aromatic) aldehydes are decarbonylated by heating with di-tert-peroxide or other peroxides, usually in a solution containing a hydrogen donor, such as a thiol. The reaction has also been initiated with light, and thermally (without an initiator) by heating at 500°C. 

Dropwise addition of the amine to the salt led to an explosion (possibly initiated by heat liberated by complex formation). 

In spite of extensive cooling and precautions, a mixture of methyl azide, methanol and dimethyl malonate exploded violently while being sealed into a Carius tube. The vapour of the azide is very easily initiated by heat, even at low concentrations. 

Elliot, M. A. et al., Kept. Invest. No. 4169, Washington, US Bin. Mines, 1948 Tests of sensitivity to initiation by heat, impact, shock or ignition sources were made on mixtures of a variety of absorbent materials containing a stoicheiometric amount of 40-70% perchloric acid. Wood meal with 70% acid ignited at 155°C and a mixture of coal and 60% acid which did not ignite below 200° C ignited at 90° C when metallic iron was added. Many of the mixtures were more sensitive and dangerous than common explosives. 

Oxidation of the durene derivative to benzenehexacarboxylic acid (mellitic acid) in an autoclave is normally effected in stages, initially by heating at 80-104°C with the vent open to allow escape of the evolved gases. Subsequent heating to a higher temperature with the vent closed completes the reaction. On one occasion omission of the first vented heating phase led to explosive rupture of the autoclave at 80° C. 

Titanium and vanadium nitrides may be prepared by a metathesis reaction of their tetrachlorides with the nitride, initiated by heat or friction. The reaction is potentially explosive. Other transition metal halides may cause ampules to explode after thermal initiation when anhydrous and were invariably found to do so when the hydrates were used. 

Mixtures of sodium nitrite and various cyanides [1] explode on heating, including potassium cyanide [2], potassium hexacyanoferrate(III), sodium pentacyanonitro-sylferrate(II) [3], potassium hexacyanoferrate(II) [4], or mercury(II) cyanide [5], Such mixtures have been proposed as explosives, initiable by heat or a detonator [5],... 

Red Phosphorus smoke mix production. Evaluation of the Sprout Waldron 35 cubic foot Jet Airmix unit for production of Red Phosphorus (RP) M8E1 Smoke Mixtures was conducted (12). Results indicated the mix was stabile and not easily initiated by heat, but sensitive to friction and snark stimuli. The burning time was slow with dense smoke emission. 

Although thermal decomposition (and runaway) is often identified with the inherent reactivities of the chemicals involved, it must be emphasized that hazards can arise from induced reactions as discussed in Chapter 2. These induced reactions may be initiated by heat, contamination, or mechanical means (e.g., shock, friction, electrostatic spark). 

Photochemical reactions are the reactions of excited-state molecules initiated by photon absorption whereas thermal reactions are the reactions of ground-state molecules usually initiated by heat. The energy of photoexcitation of molecules can be provided by photon absorption even at very low temperatures and is of the same order as the activation energies for ground-state molecules. Provided the process of photoexcitation can be utilised in order to... 

Relationships existing between structure, stability and thermal, photochemical and explosive decomposition (sometimes spontaneous) of the inorganic azides has been extensively investigated and reviewed [1,2]. The ignition characterisitcs of explosive inorganic azides, with or without added impurities under initiation by heat or light have been discussed [3],... 

Intimate mixtures of chlorates, bromates or iodates of barium, cadmium, calcium, magnesium, potassium, sodium or zinc, with finely divided aluminium, arsenic, copper carbon, phosphorus, sulfur hydrides of alkali- and alkaline earth-metals sulfides of antimony, arsenic, copper or tin metal cyanides, thiocyanates or impure manganese dioxide may react violently or explosively, either spontaneously (especially in presence of moisture) or on initiation by heat, friction, impact, sparks or addition of sulfuric acid [1], Mixtures of sodium or potassium chlorate with sulfur or phosphorus are rated as being exceptionally dangerous on frictional initiation. 

Many of the salts of peroxoacids are unstable or explosive, are capable of initiation by heat, friction or impact, and all are powerful oxidants. Individually indexed compounds are ... 

Autoxidation. Self-catalyzed oxidation in the presence of air. Autoxidation can be initiated by heat, light, or a catalyst. The commercial production of phenol and acetone from cumene is autoxidation. Other examples include the degradation of polymers exposed to sunlight for long periods of time gum formation in lubricating oils and gasoline and the spoilage of fats. 

M.A. Cook etal, TrFaradSoc 56, 1028-38(1960 Promotion of shock initiation of detonation by metallic surfaces) 36a) Andreev Belyaev (i960), 265-68 (Starting impulse and mechanism of initiation) 268-70 (Initiation by heat) 270-73 (Initiation by flame) 273-86 (Initiation by shock or friction) 287-89 (Initiation of expln in projectiles on hitting a target) 36b) J. Favier C. Fauquignon, MP 42, 65-81(1960) (Initiation of expls. and transmission of detonation) 37) D.B. Moore J.C. Rice, Detonation of Secondary Explosives by Lead Azide , SRI (Stanford Research Institute), Poulter Laboratories, Technical Report 004-60(1960) 37a) S.J. Jacobs, AmRocket-... 

Initiation by Heat. See Thermal Explosion and Ignition Hot Spots in this Vol... 

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