Nucleophilic substitution in halogenoalkanes
No description yet. This curated deck is ready for daily study.
Card preview (16)
What is a nucleophile? (spcs. frms. cvlnt. bnd. - dntng. E pr.)
A species that forms a covalent bond by donating an electron pair
What are the three common nucleophiles in organic chemistry?
Hydroxide ion - :OH- Ammonia - :NH3- Cyanide ion - :CN-
What type of reaction do nucleophiles undergo with halogenoalkanes?
Nucleophilic substitution reaction
What can halogenoalkanes take part in nucleophilic substitution reactions? (H = >elcngtv. thn. C - frm. plr. bnds, rct. w. nclphls. - act. elctrphls.)
Halogens are more electronegative than carbons, so they form polar bonds. When they react with nucleophiles, they can act as electrophiles
How would you measure the rate of reaction of halogenoalkanes? (plce. h bkr, dslve, H usng. ethnl, add AgNO3 + H2O - msre. tme. tks. prcpte. frm.)
Place each halogenoalkane into beaker. Dissolve halogenoalkane using ethanol. Add silver nitrate and water, then measure the time it takes for precipitate to form.
What determines the rate of reaction of halogenoalkanes?
The bond enthalpy
Which halogen is most reactive and why? (I - lwst. BE - rqrs. lss. E rctn. tke. plce.)
Iodine because it has the lowest bond enthalpy, so it requires less energy for a reaction to take place
What reagent and conditions are needed for the nucleophilic substitution reaction with hydroxide ions? (-OH)
Reagent = Aqueous sodium or potassium hydroxide (NaOH/KOH) Conditions = being heated under reflux
When a halogenoalkane undergoes nucleophilic substitution with hydroxide, what is formed?
An alcohol is formed
Why is the reagent used in the nucleophilic substitution reaction with a cyanide ion, dissolved in ethanol and not water? (usng. wtr. = alc. frm. alngsde. N - ethnl ensrs. ntrls. frm.)
By using water, alcohols may form alongside nitriles, so ethanol ensures only nitriles form
What is the suitable reagent and condition needed for a nucleophilic substitution reaction with a cyanide ion? (-CN)
Suitable reagent = ethanolic potassium/sodium cyanide (KCN/NaCN) Conditions = heated under reflux
When a halogenoalkane undergoes nucleophilic substitution with a cyanide ion, what is formed?
A nitrile is formed
What is the suitable reagent and condition needed for a nucleophilic substitution reaction with ammonia? (:NH3)
Excess ethanolic ammonia, high pressure and heat
Why is excess ammonia needed to halogenoalkanes to amines? (A = Nucs. - rct. w/ H - frm. sec./trtry. A)
Amines can act as nucleophiles, reacting with halogenoalkanes to form secondary and tertiary amines
When a halogenoalkane undergoes nucleophilic substitution with ammonia, what is formed?
An amine is formed
Draw the full mechanisms for a hydroxide ion reacting with an alkyl halide and name the desired conditions/reagents: 1/ 2-iodo-3-methylbutane reacts with aqueous sodium 2/ bromocyclohexane reacts with aqueous potassium Draw the full mechanisms for a cyanide ion reacting with an alkyl halide, and name the desired conditions/reagents: 1/ chloroethane reacts with potassium cyanide 2/ 2-bromopropane reacts with potassium cyanide Draw the full mechanisms for ammonia reacting with an alkyl halide, and name the desired conditions/reagents: 1/ bromoethane reacts with ammonia 2/ 2-chloro-3methylbutane reacts with ammonia
ANSWERS - mechanisms for a hydroxide ion reacting with an alkyl halide: 1/ 2-methylbutan-2-ol 2/ cyclohexanol (condtions: heat, ) ANSWERS - mechanisms for a cyanide ion reacting with an alkyl halide: 1/ propanenitrile 2/ 2-methylpropane nitrile ANSWERS - mechanisms for a cyanide ion reacting with an alkyl halide: 1/ methylamine 2/ 2-methylbutylamine