17 - alcohols, esters and carboxylic acids Flashcards
alcohols general formula
CnH2n+1OH
alcohols functional group
hydroxyl group, OH
naming alcohols
add -anol to stem
location of OH in name (propan-2-ol)
primary alcohol
an alcohol in which the carbon atom is bonded to the OH group is attached to one other carbon atom/alkyl group
secondary alcohol
an alcohol in which the carbon atom is bonded to the OH group is attached to two other carbon atoms/alkyl groups
tertiary alcohol
an alcohol in which the carbon atom is bonded to the OH group is attached to three other carbon atoms/alkyl groups
alcohols with two OH groups
-diol
alcohol properties
. higher boiling points than expected (H bonding)
. smaller alcohols are miscible in water (H bonding)
. alcohols are weaker acids than water
. have a small degree of dissociation
degree of dissociation
the extent to which a molecule of an acid ionises in a solvent to produce H+ ions or the extent to which a base produces OH- ions in a solvent
ethanol dissociation in water
C2H5OH <=> C2H5O- (ethoxide ion) + H+
. equilibrium position at left
more alkyl groups of an alcohol = stronger/weaker acid?
weaker acid
reactions to make alcohols
. electrophilic addition of steam to an alkene (H3PO4 catalyst)
C2H4 + H2O => C2H5OH
. oxidation of alkenes with cold, dilute, acidified potassium maganate to form a diol
C2H4 + H2O + [O] => HOCH2CH2OH
. nucleophilic substitution (hyrolysis) of a halogenoalkane by heating with NaOH
CH3CH2Br + NAOH => CH3CH2OH + NaBr
. reduction of an aldehyde (primary alcohol) or ketone (secondary alcohol) using a reducing agent
CH3CH2CHO + 2[H] => CH3CH2CH2OH
CH3COCH3 + 2[H] => CH3CH(OH) CH3
. reduction of a carboxylic acid using a reducing agent
CH3COOH + 4[H] => CH3CH2OH +H2O
. hydrolysis of an ester by heating with a dilute acid or alkali
reducing agent
. NaBH4
. LiAlH4
alcohol reactions
. combustion
. substitution to form a halogenoalkane
. reaction with a sodium metal
. esterification
. hydrolysis of esters
. dehydration
. oxidation
alcohol reactions: combustion
alcohol + oxygen => CO2 + H2O
alcohol reaction: substitution to form a halogenoalkane
alcohol + hydrogen halide => halogenoalkane + water
. in situ - in a reaction vessel
. heated under reflux
. haloalkane distilled off + collected as oily droplets
. HCl made in situ
. HBr made using KBr or conc. sulfuric acid
. SOCl2 can be used (HCl, SO2 formed)
. P can be used (HX, POX3), PCl3 needs heating
alcohol reaction: reaction with sodium metal
alcohol + sodium => sodium alkoxide + hydrogen
. longer the hydrocarbon chain = less vigorous the reaction with sodium metal
alcohol reaction: esterification
. a reaction of a carboxylic/ acyl chloride with an alcohol/phenol to produce an ester and small molecules
. carboxylic acid + alcohol <=> ester + water
. ‘alcohol-yl carboxylic acid- noate’
alcohol reaction: ester hydrolysis
. heating under reflux with acid/base
. acid:
—-reversible
—-ester + water => carboxylic acid + alcohol
AND PRESENT AFTER REACTION
. alkali:
—-fully hydrolysed
—-not reversible reaction
—-ester + NaOH => alcohol + sodium salt
alcohol reaction: dehydration
. type of elimination reaction
. reaction in which water is removed from larger molecules
. alcohol => (heat and catalyst) alkene + water
—–catalyst = Al2O3/pumic/conc. acid, hot
—–alcohol vapour
alcohol reaction: oxidation
. K2Cr2O7 oxidises only primary and secondary alcohols
. primary - forms aldehyde, carboxylic acid, GREEN
. secondary - forms ketone, GREEN
. tertiary - nothing, REMAINS ORANGE
reactions to make carboxylic acids
. primary alcohol + potassium magnate solution
. nitrile + HCl
carboxylic acid, acidic properties
. weak acids
. CH3COO ethanoate ion
. usual acid reactions
carboxylic acids, reduction
. LiAlH4 is reducing agent
. use [H] symbol instead
. primary alcohol + water is the product
