Halogenalkanes

• Reagents that attach and form bonds with positively charged carbon atoms 
• Either negatively charged ions or has atoms with partial negative charges 
• Has one lone pair - used to form covalent bonds = donate to electron deficient 

Attach carbon atoms of carbon - halogen causes electron pair on Nu attracted to small positive charge on carbon 

Electrons in C-X bond repelled as Nu approached carbon 

Nu bond to carbon + C-X breaks 

Two electons move to halogen ➡️ halide ion 

Conditions - warm aqueous sodium hydroxide (source of OH ion) + carried out under reflux 

The C- X breaks - both electons move from bond ➡️ halogen 

New bond formed ↔️ OH ion + carbon 

Alcohol formed 

Overall reaction: 

R-X + NaOH ➡️ ROH + NaX 

R = alkyl group 

X = halogen 

Conditions - warm ethanolic potassium cyanide (source of N ions) + carried out under reflux 

Nitrile formed 

Overall:

R-X + KCN ➡️ RCN + KX 

Conditions - heat with ethanolic ammonia  + must have excess ammonia 

Amine produced (identify by fishy smell) 

Ammonia ions ( NH4+) also produced 

In second phase another molecule of NH3 acts as base by reacting with hydrogen = why excess NH3 needed 

Overall: 

CH3CH2Cl + 2NH3 ➡️ CH3CH2NH2 + NH4Cl

React via elimination using ethanol solvent 

Conditions - warm ethanolic sodium hydroxide + carried out under reflux 

OH attracts H ion on carbon adjacent to carbon with halogen. OH acts as base forming water 

Overall:

CH3CHClCH3 + KOH ➡️ CH2CHCH3 + H2O + HCl

Alkene formed when using ethanol 

Alcohol - using water 

⬆️ down group - bond strength/entahlpy determine reactivity not bond polarity 

C-F = 485 

C-Cl = 327 

C-Br = 285

C-I = 213 

C-I has lowest bond enthalpy + easiest to break - with C-I more reactivity