Bond homolytic fission

Inorg anic Compounds. Hydrogen chloride reacts with inorganic compounds by either heterolytic or homolytic fission of the H—Cl bond. However, anhydrous HCl has high kinetic barriers to either type of fission and hence, this material is relatively inert. 

Photochemical Reactions. The photochemistry of chlorine dioxide is complex and has been extensively studied (29—32). In the gas phase, the primary photochemical reaction is the homolytic fission of the chlorine—oxygen bond to form CIO and O. These products then generate secondary products such as chlorine peroxide, ClOO, chlorine, CI2, oxygen, O2, chlorine trioxide [17496-59-2] CI2O2, chlorine hexoxide [12442-63-6] and... 

The low bond-strength of the O—0 bond renders peroxides susceptible to homolytic fission to give oxy radicals on heating. Diacyl peroxides give rise to acyloxy radicals which then decompose to aryl radicals and carbon dioxide, Eq. (5). For example, dibenzoyl... 

Platinum removes a halogen atom from the halide, causing homolytic fission of the C-halogen bond. The resulting Pt -XR radical pair can either react to form Ptn(R)X or separate, with subsequent reaction with RX leading to either PtX2 or PtRX species or reaction with solvent molecules. 

The material is arranged as follows. Photochemical reactions are discussed first (Section VI,A) as they represent the most thoroughly studied and only definitely established examples of the simplest type of reaction, viz., the homolytic fission of the Co—C bond. Thermal (i.e., nonphotochemical)... 

Thermal insertion occurs at room temperature when R is XCH2CHAr-, at 40° C when R is benzyl, allyl, or crotyl (in this case two isomeric peroxides are formed), but not even at 80° C when R is a simple primary alkyl group. The insertion of O2 clearly involves prior dissociation of the Co—C bond to give more reactive species. The a-arylethyl complexes are known to decompose spontaneously into CoH and styrene derivatives (see Section B,l,f). Oxygen will presumably react with the hydride or Co(I) to give the hydroperoxide complex, which then adds to the styrene. The benzyl and allyl complexes appear to undergo homolytic fission to give Co(II) and free radicals (see Section B,l,a) in this case O2 would react first with the radicals. 

Homolytic fission of an R3C—X bond is, in the gas phase, always less energy-demanding than heterolytic fission. This energetic advantage is, however, often reversed in polar solvents, because of the energy then developed—in heterolytic fission—from solvation of the developing ions. 

This reflects the relative ease with which the C—H bond in the alkane precursor will undergo homolytic fission, and more particularly, decreasing stabilisation, by hyperconjugation or other means, as the series is traversed. There will also be decreasing relief of strain (when R is large) on going from sp3 hybridised precursor to essentially sp2 hybridised radical, as the series is traversed. The relative difference in stability is, however, very much less than with the corresponding carbocations. 

Another dinuclear carbonyl which presents interesting problems is ](ri C5H5)Fe(CO) ] 2 Does the photochemistry proceed exclusively through homolytic fission to produce two (13 -05 )Fe-(C0)2 radicals or by other possible routes The discussion of this reaction has involved mechanistic and synthetic studies (77), flash photolysis (78) and low-temperature photolysis (29) - the latter work, in THF or ethyl chloride at -78°C, invokes an intermediate in which the Fe-Fe direct bond is broken but the two halves of the molecule are held together by a CO bridge. Clearly such an intriguing problem merits more detailed investigations. 

When a covalent bond breaks to produce radicals, i.e. one electron of the bond pair goes to each atom, homolytic fission has occurred. These highly reactive chlorine radicals attack the methane molecules. 

There are cases where racemisation takes place under the influence of heat. Under such conditions there is homolytic fission of the bond between the asymmetric carbon atom and one of the substituents. The radical formed may assume either of the two enantiomeric configurations with equal possibility of recombination, giving a racemate. For example a chloroethyl benzene during distillation undergoes thermal racemisation, but in presence of lewis acids it undergoes racemisation with the intermediate formation of a carbocation. 

The species -CH3 and -CH3CO are radicals species containing unpaired electrons. Radicals are formed by homolytic fission of a covalent bond, where the electron pair constituting the bond is redistributed such that one electron is transferred to each of the two atoms originally joined by the bond. 

In any reaction in chemistry, bonds in the reactants are broken and bonds in the products are made. The process of breaking bonds is known as bond fission and there are two types of bond fission homolytic fission and heterolytic fission. 

This bond-breaking process is known as homolytic fission because two species of the same charge (neutral) are formed. Such fission normally occurs when non polar covalent bonds are broken. You will notice that each fragment produced has an unpaired electron and can therefore be described as a free radical. 

Homolytic Bond Fission Reactions. The homolytic fission of a chemical bond... 

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