alcohol to halogenoalkane?

i know the nucleophilic substitution reaction between a halogenoalkane and aqueous KOH gives an alcohol... but i always forget, how to you go backwards?

for example, what are the reagents/conditions for the conversion of butan-1-ol to 1-bromobutane??

thanks

Reply 1

kpg

HBr (made in situ by heating conc. sulphuric acid and NaBr) will give you a Bromoalkane.

Red phorsphorus iodide will give you the iodoalkane

PCl5 will give you the chlroalkane

Reply 2

cjoc28

kpg

HBr (made in situ by heating conc. sulphuric acid and NaBr) will give you a Bromoalkane.

Red phorsphorus iodide will give you the iodoalkane

PCl5 will give you the chlroalkane

thanks. are the last two room temp?

Reply 3

Ramaya

cjoc28

HBr_(aq)
NaBr_(s) and conc. H₂SO₄
Heat under reflux

Reply 4

Magician

depends what you are making.

react PCl5 with an alcohol to make chloroalkane

C2H5OH + PCl5 ---> C2H5Cl + HCl + POCl3
conditions: at room temp. and alcohol must be dry

react solid sodium bromind and conc. sulphuric acid to give bromoalkane

NaBr + H2SO4 --> HBr + NaHSO4
then HBr + C2H5OH --> C2H5Br + H2O
conditions: add H2SO4 mixed with alcohol to solid NaBr @ room temp

react phosphorus and iodine to give iodoalkane:

2P + 3I2 --> 2PI3
then 3C2H5OH + PI3 --> 3C2H5I + H3PO3
conditions: add the alcolod to a mixture of moist red phosphorus and iodine @ room temp