Alcohols Flashcards
Example of alcohol name with more than one OH:-
Ethan-1,2-diol
What is the stability order of alcohols?
3o>2o>1o
Primary alcohol:-
Carbon bonded to OH is bonded to one carbon.
Secondary alcohol:-
Carbon bonded to OH is bonded to 2 carbons
Tertiary alcohol:-
Carbon bonded to OH is bonded to 3 carbons
What does O in square brackets represent?
Oxidising agent
How do you name an aldehyde?
Use root (e.g meth) with -anal i.e. Methanal
What is obtained by alcohol reaction with an oxidising agent?
Aldehyde/ketone and H2O
How do you name ketones?
Root -an one
E.g. Propanone
Aldehyde functional group:-
C with x bond, double bond to O and single bond to H
Ketone functional group:-
C with two single C bonds and a double O bond
What can be oxidised to a carboxlylic acid?
Aldehyde
Aldehyde/alcohol/ketone test:-
1) Add 1cm depth of each solution to a separate test tube.
2) Add 1cm depth potassium dichromate and 2cm depth of dilute sulfuric acid. Mix thoroughly.
3) Heat each gently in a water bath, pointing away from face.
4) note observations.
Test results for tertiary alcohol:-
Not oxidised (stayed orange) + relatively high boiling point.
Test results for primary alcohol:-
Oxidised (green) + relatively high boiling point.
Test results for ketone:-
Stays orange- can’t be oxidised further as would require breaking C-C bonds
Aldehyde test result:-
Oxidised to carboxylic acid (orange to green)
Aldehyde and ketone boiling boints relative to alcohols
Relatively lower due to alcohols’ hydrogen bonding.
Aldehyde and ketone boiling boints relative to alkanes
Relatively higher due to alkanes’ weak induced dipole-dipole attractions.
Why is ethanol a polar molecule?
O is v. electromagnetic so delta neg and consequently the other atom become delta pos. Non-symmetrical dipole distribution and a permanent dipole lead to a polar molecule.
Why is ethanol boiling point higher than propane boiling point?
H only has 1 electron and when pulled away acts like a proton. V. delta pos so V. attracted to lone pair of O on other molecule..
What gives a carboxylic acid (and water)?
Prolonged oxidation of a primary alcohol with excess oxidising agent.
Carboxylic acid functional group:-
C with double bonded O and single OH.
Naming alcohols:-
Use alkane root with -an and the number of where the OH is. Number inbetween this and ‘ol’
E.g propan-2-ol
Experimental technique using liebig condenser:-
Reflux
Refluxing:-
Boiling then condensing repeatedly
2 benefits of reflux:-
Prevents loss by evaporation and allows prolonged oxidation
What is needed to dehydrate alcohol:-
H atom on carbon adjacent to C-OH
Secondary alcohol to ketone conditions:-
Heat w/ aqueous acidic K2Cr2O7
Primary alcohol to carboxylic acid:-
Prolonged heating under reflux with aqueous acidic K2Cr2O7 in excess.
Primary alcohol to aldehyde:-
Heat with aqueous acidic K2Cr2O7 and distill product off at once to prevent further oxidation.
