HALOALKANES

reactivity of haloalkanes. More reactive due to polarisation of C-halogen bond. C (electron-deficient, readily attacked by nucleophiles) -X (more EN). saturated: main rxn Nu- substitution. reactivity R-X towards Nu-: 2 factors: 1. strength C-X bond (important for rate substitution). C-F 467, C-Cl 346, C-Br 290, C-I 228 2. partial +ve. due to increase stregth of C-X bond when size decrease,

• R-I > R-Br > R-Cl > R-F (most polarised)
• R-I < R-Br < R-Cl < R-F (most polarised)

hydrolysis. R-X + NaOH (OH- Nu-) heat (boiled under reflux) -> R-OH (alcohol) + NaX chlorocyclohexane -> cyclohexanol. Due to: 1. bigger size X, 2. weaker C-X bond, 3. reactivity increase rate rxn hydrolysis…

• R-Cl < R-Br < R-I (more reactive)
• (more reactive) R-Cl > R-Br > R-I

hydrolysis of polysubstituted haloalkane. 1,2-dibromoethane + 2NaOH (boil) -> 1,2-ethanediol + 2NaBr. But 1,1-dibromomethane + NaOH (boil) -> ethanal (aldehyde)??

• because: first produce 1,1-ethanediol (-OH attach same C, NOT STABLE, decompose to ethanal via elimination of H2O).
• because: first produce 1,1-ethanediol (-OH attach same C, STABLE, decompose to ethanal via elimination of H2O).

test for 1-chlorobutane and 1-iodobutane

• use silver nitrate, AgNO3 -> AgCl (white precipitate). -> AgI (yellow ppt).
• use silver nitrate, AgNO3 -> AgCl (yellow ppt). -> AgI (white precipitate).

hydrolysis of polysubstituted haloalkane. 1,2-dibromoethane + 2NaOH (boil) -> 1,2-ethanediol + 2NaBr. But 1,1-dibromomethane + NaOH (boil) -> ethanal (aldehyde)??

• because: first produce 1,1-ethanediol (-OH attach same C, NOT STABLE, decompose to ethanal via elimination of H2O).
• because: first produce 1,1-ethanediol (-OH attach same C, STABLE, decompose to ethanal via elimination of H2O).

test for 1-chlorobutane and 1-iodobutane

• use silver nitrate, AgNO3 -> AgCl (white precipitate). -> AgI (yellow ppt).
• use silver nitrate, AgNO3 -> AgCl (yellow ppt). -> AgI (white precipitate).

test for 1-chlorobutane and 1-iodobutane

• use silver nitrate, AgNO3 -> AgCl (white precipitate). -> AgI (yellow ppt).
• use silver nitrate, AgNO3 -> AgCl (yellow ppt). -> AgI (white precipitate).

test for 1-chlorobutane and 1-iodobutane

• use silver nitrate, AgNO3 -> AgCl (white precipitate). -> AgI (yellow ppt).
• use silver nitrate, AgNO3 -> AgCl (yellow ppt). -> AgI (white precipitate).

reactivity towards Nu- subs.: haloarenes vs haloalkanes

• delocalisation reduce partial +ve charge on halogen-carrying C atom making it less susceptible to attack by Nu-.
• delocalisation increase partial +ve charge on halogen-carrying C atom making it less susceptible to attack by Nu-.

reactivity of haloalkanes. More reactive due to polarisation of C-halogen bond. C (electron-deficient, readily attacked by nucleophiles) -X (more EN). saturated: main rxn Nu- substitution. reactivity R-X towards Nu-: 2 factors: 1. strength C-X bond (important for rate substitution). C-F 467, C-Cl 346, C-Br 290, C-I 228 2. partial +ve. due to increase stregth of C-X bond when size decrease,

• R-I > R-Br > R-Cl > R-F (most polarised)
• R-I < R-Br < R-Cl < R-F (most polarised)