Halogenoalkanes Flashcards
-general formula for halogenoalkanes
CnH(2n+1)X
-define Primary halogenoalkane
-One carbon attached to the
carbon atom adjoining the
halogen
-define Secondary halogenoalkane
Two carbons attached to the
carbon atom adjoining the
halogen
-define Tertiary halogenoalkane
Three carbons attached to the carbon atom adjoining the halogen
-define nucleophile
electron pair donator e.g. :OH-, :NH3, CN
-what do the nucleophile do in NUCLEOPHILIC SUBSTITUTION?
-replace the halogen in a halogenoalkane.
-give three examples of nucleophiles
:OH-
:CN-
:NH3
describe the strength of the C-X bond
the weaker the bond, the easier it is to break and the faster the reaction
e.g: Iodoalkanes are the fastest to substitute and fluoroalkanes are the slowest. The strength of the C-F bond is such that fluoroalkanes are very unreactive
describe the nucleophillic substitution with aqueous hydroxide ions
reagent–> NaOH, KOH
conditions–> in warm aqueous solution, , under reflux
mechanism: nucleophillic substitution
type of reagent: nucleophile: OH
Overall equation: R-X + NaOH →R-OH + NaX
describe the nucleophillic substitution with cyanide ions
reagent–> KCN
Conditions–> ethanolic and warm solution, under refluc
mechanism: nucleophillic substituion
type of reagent—> nucleophile: CN
Overall equation: R-X + KCN → R-CN + KX
describe the nucleophillic substitution with ammonia
reagent–> NH3 dissolved in ethanol
conditions–> Excess ammonia dissolved in ethanol at pressure in a sealed container.
mechanism: nucleophillic substiution
type of reagent—> nucleophile : NH3
describe the elimination with alcoholic hydroxide ions
reagent–> Potassium (or sodium) hydroxide
Conditions: In ethanol ; heat
Mechanism: Elimination
Type of reagent: Base, OH-
