(Fox& Whitesell, 2013).
Thebond dissociation energies also abbreviated as BDE shows the amountof energy needed to break a specific bond in a specific molecule,while the calculations of average bond are performed fromexperimental data set with the assumption that all C-H bonds haveequal energy (Fox & Whitesell, 2013).
Breakof bonds normally requires heat. This heat energy is termed as bonddissociation energy. The formation of radicals is through hemolyticcleavage. The process through which a bond breaks and leave theelectrons similarly divided between atoms is known as hemolysis andhemolytic cleavage. Species with more than an atom as well asunpaired electron is known as radicals. Free atoms and radicals existas intermediates in trivial centration in various reactions howevercannot be isolated (Fox & Whitesell, 2013).
Reactionbetween steam and carbon monoxide gives hydrogen gas and carbondioxide.
H2O (g) + CO (g) H2 (g) + CO2 (g)
Wecan achieve the calculation as shown in the diagram
Theroutes can now be equated and the equation solved to get the reactionchange .
ΔH= 1077 + 2(464) – 2(805) – 436
ΔH+ 2(805) + 436 = 1077 + 2(464)
ΔH= -41 kJ mol-1
Reactionbetween ethane and Chlorine
Ethanereacts with chlorine to give hydrogen chloride and chloroethanegases.
Fromthe equation above the bod of Cl-Cl and C-H are broken to create new H-Cl and C-Cl bond (Fliszár,2014).
Theenergy required to break Cl-Cl and C-H is
+243+ 413 = +656 kJ mol-1
Theamount of released energy during the creation of C-Cl as well as H-Clis
-432– 346 = – 778 kJ mol-1
Therefore,the net change is -778 + 656 = -122 kJ mol-1
Thechlorination of 2-methylpropaneunder the presence of UV light gives the following
Cl2 + (CH3)3CH——>35% (CH3)2CHCH2Cl+ 65% (CH3)3CCl
Fromthe two steps that create, free radical chain reaction forhalogenation, the first step is a product-determining step (hydrogenabstraction). After the formation of a carbon radical, the nextbonding of a halogen atop occurs only at the radicle site
InitialPhase:       X•R3C-H   ——> H-X + R3C•
Secondphase:     R3C•  +   X2  ——> X•+ R3C-X
R–H  +   energy   ——>  R• + H•
Thebond decisions energies within alkanes reduces with the progression.
Methane> Primary > Secondary > Tertiary.
Fliszár,S. (2014). Atoms,Chemical Bonds and Bond Dissociation Energies.Berlin, Heidelberg: Springer Berlin Heidelberg.
Fox,M. A., & Whitesell, J. K. (2013). Organicchemistry.Sudbury, Mass. [u.a.: Jones and Bartlett.