4.2.1 alcohols
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what is the shape and bond angle around the O and why
bent 104.5° repulsion between two bond pairs and two lone pairs
what intermolecular forces are involved in alcohols
permanent dipole, hydrogen bonding
what properties does the hydrogen bonding cause in alcohols
• low volatility • high m.p and b.p due to strong hydrogen bonding • able to dissolve in water due to hydrogen bonds that can bond to water
what happens when alcohols are combusted in excess oxygen
complete combustion
in an oxidation reaction what is the reagent also called as
oxidising agent
what is the reagent in oxidation reactions with alcohol
potassium dichromate K2Cr2O7
what distils first and why aldehydes or alcohols
aldehydes as alcohols have hydrogen bonding whereas aldehydes have permanent dipole-dipole
describe reflux condition
• continual evaporation and condensing of organic reagents • end of the condenser is left open to prevent explosion from pressure build-up • a water bath or electric heater is used as the organic reagent is flammable • anti-bumping granules are used to prevent vigorous uneven boiling
what is distillation used for
separating organic product from reagent
what condition and reagent is needed to form an aldehyde from a primary alcohol in an oxidation reaction
distillation and k2cr2o7/h2so4
what is the general equation when a primary alcohol forms an aldehyde in an oxidation reaction
ch3ch2oh + [o] —> rhco + h2o
describe the identification test for primary alcohols
add k2cr2o7 observe a yellow to green colour change as dichromate ion (cr2o7-2) reduced to cr+3 ion the product is then distilled and tested with Tollen’s reagent observe a silver mirror
what condition and reagent is needed to form a carboxylic acid from a primary alcohol in an oxidation reaction
reflux and k2cr2o7/h2so4
what is the general equation when a primary alcohol forms a carboxylic acid in an oxidation reaction
rch2 + 2[o] —> rcooh + h2o
describe the identification test for a carboxylic acid
add sodium carbonate Na2CO3 observe effervescence
what condition and reagent is needed to form a ketone from a secondary alcohol in an oxidation reaction
reflux and k2cr2o7/h2so4
what is the general equation when a secondary alcohol forms a ketone in an oxidation reaction
rchohr + [o] —> rcor + h2o
describe the identification test for a secondary alcohol
add k2cr2o7 observe a yellow to green colour change as dichromate ion (cr2o7-2) reduced to cr+3 ion the product is then distilled and tested with Tollen’s reagent observe no change
why can tertiary alcohols not undergo oxidation reactions
they are resistant because there is no h-c with the oh group, they can be combusted but will not react with k2cr2o7
describe the identification test for a tertiary alcohol
add k2cr2o7/h2so4 no observational change
why are anti bumping granules added when distilling and using reflux
prevent vigorous uneven boiling
how is tollen’s reagent formed
mixing aqueous ammonia and silver nitrate to make [ag(nh3)2]+
what is elimination / dehydration
the loss of an atom or group of atoms from a molecule
what are the conditions and the reagent in elimination of alcohols
reflux and concentrated h2so4 or h3po4