Combustion (not difficult) C(n)H(2n+2) + (n+1)O2 ----> n(CO2) + (n+1)H2O Halogenation (More difficult) Three Step Mechanism: Example used is C2H6 + Cl2 ----> C2H5Cl +HCl Step 1: Initiation UV light used to split the diatomic halogen (eg. Cl2) into two free radicals (eg. 2Cl•). This is Homolytic Fission UV light Cl2 ----> 2Cl free radicals
Step 2: Propogation Really two reactions: 1) Cl•(g) + H-CH2CH3 ----> HCl + •CH2CH3 (free radical) This radical is then used in the following reaction 2) •CH2CH3 + Cl2 ------> Cl-CH2CH3 +Cl• (Cl• is regenerated)
Step 3: Termination When the Cl2 or C2H6 have run out the remaining free radicals will join together. This can take 3 forms Cl• +Cl• ----> Cl2 Cl• + •CH2CH3 -----> Cl-CH2CH3 •CH2CH3+ •CH2CH3 -----> C4H10 To Alkanes: CnH2n +H2 + (Nickel Catalyst) ----> CnH(2n+2) To di-Halogenoalkanes: (two halogens) CnH2n + Br2 ----> CnH2nBr2 (The C=C bond is broken and each of those carbons ios now bonded to one Halogen) To mono-Halogenoalkanes: CnH2n + HBr ----> CH3CH2Br To Alcohols: CnH2n + H2O(g) + phosphoric acid catalyst ---------> CnH2n+1OH Alcohols Combustion: CnH(2n+1)OH + (1.5n)O2 -------> nCO2 + (n+1)H2O To Alkenes: CnH(2n+1)OH +conc. H2SO4 (catalyst) --------> CnH2n +H2O To Esters: Add carboxcylic acid, acid catalyst and heat. For primary alcohols: To Aldehydes: add acid and potassium dichromate, distil. To Carboxcylic acids: add excess acid and potassium dichromate, reflux. Secondary Alcohols: To Ketones: add acid andd potassium dichromate, heat. |
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