Mechanisms

• Radical substitution involves the substitution of one hydrogen from the cyclohexane with one chlorine, carried out under UV light.
• The mechanism of radical substitution operates via three steps: initiation, propagation, and termination.
• In the initiation step, UV light splits the covalent bond between the two chlorine atoms into two free radicals, represented by the unpaired electron.
• In the propagation steps, a chlorine radical strips out a hydrogen to generate HCl, and the leftover radical feeds into propagation.
• Termination involves combining any two radicals that have been produced in the mechanism.
• Electrophilic addition involves the reaction of cyclohexane with chlorine, resulting in an addition reaction where two reactants become one product.
• The chlorine molecule is nonpolar because of the identical electronegativity in the two seals, but as it gets closer to the carbon-carbon double bond, the electron density around the chlorine is repelled towards the right, creating a dipole across the molecule that can act as an electrophile and electron pair acceptor.
• In electrophilic addition, a pair of electrons from the double bond are attracted to the chlorine, breaking the bond and resulting in heterolytic fission, forming a carbocation and a chloride ion.
• In the second example, propanol reacts with Nabh4, forming a secondary alcohol.
• Nabh4 acts as a nucleophile, donating a pair of electrons to the slightly positive carbon, which repels the PI electron pair and the CCL bond, forming an unstable intermediate.
• A water molecule is brought into play, forming a bond with the hydrogen, generating the product.
• In the final example, one chloral reacts with KCN in ethanol, forming a nitrile.
• Sodium cyanide and sulfuric acid react together to form HCN, which reacts with propane, forming two hydroxy nitrile.
• The mechanism of this reaction is very similar to the previous two, with a pair of electrons from the nucleophile attracted to the carbon, repelling the PI electron pair and the CCL bond, forming an intermediate.
• A water molecule is brought into play, forming a bond with the hydrogen, generating the alcohol product.
• The chloride ion then attaches itself to the positively charged carbon, resulting in the product, 1,2-dichloro cyclohexane.
• Nucleophilic substitution involves the reaction of chloro cyclohexane with the hydroxide ion, resulting in a substitution reaction where the carbon chlorine bond is broken and a new bond is formed between the hydroxide ion and the carbon.
• The carbon chlorine bond in the chloro cyclohexane will have a dipole across it.
• The mechanism involves the formation of the electrophile, the electron pair acceptor, when the two concentrated acids react to form the important ion, the nitronium ion.
• In the third example of nucleophilic addition, propanol is reacted with sodium tetrahydrate or borate three, represented by the H in square brackets, resulting in the formation of a primary alcohol, propane one.
• The intermediate stabilizes itself by losing the pair of electrons in the carbon-hydrogen bond and reforming the Pi electron system
• A pair of electrons from the Pi electron cloud is attracted to the nitronium ion, forming an unstable intermediate.
• The conditions for the reaction include a catalyst, such as aluminum bromide or ferric bromide, also referred to as a halogen currier.
• The products of the reaction are nitrobenzene and an H+ ion.
• In the first example of electrophilic substitution, benzene is reacted with nitric acid, resulting in mono nitration, where one of the hydrogens on the benzene ring is replaced by the nitro group from the nitric acid, forming nitrobenzene.
• The products of the reaction are bromobenzene and an H+ ion.
• In the second example of electrophilic substitution, benzene is reacted with bromine, resulting in mono bromination, where only one hydrogen has been substituted with a bromine, forming bromobenzene.
• Because of the higher electronegativity of chlorine, the hydroxide ions can act as a nucleophile, an electron pair donor, and it will donate that pair of electrons on the oxygen to the slightly positive carbon, which will repel the pair of electrons in the carbon-chlorine bond.
• A pair of electrons from the Pi electron system is attracted to the B+ ion, forming an unstable intermediate.
• The mechanism involves the formation of the electrophile, the electron pair acceptor, when the bromine reacts with the aluminum or ferric bromide to form febr3, which then acts as the catalyst.
• The conditions for the reaction include a temperature of 50 to 55 degrees C, concentrated nitric acid and concentrated sulfuric acid catalyst.
• The products of the reaction are chlorine gas and hydroxide ions.