Aromatic compounds & Carbonyls Flashcards
how do you make an ester ?
react an alcohol with a carboxylic acid or a carboxylic acid derivative
what is a carboxylic acid derivative ?
substance made from carboxylic acid (like an acyl chloride)
how do you name an ester ?
first part of name - alkyl group
second part - carboxylic acid group, but ‘oate’ replaces ‘oic acid’
what is an esterification reaction ?
reversible reaction between alcohol and carboxylic acid to make an ester
what is needed for an esterification reaction ?
heated / concentrated sulfuric acid catalyst
as an esterification reaction is reversible, what must you do…
separate the product as its formed
describe esterification reaction for small esters
warm (product) mixture to distil off the ester as is more volatile than other compounds
define volatile
easily evaporated
what else is produced in esterification reaction
water
what type of reaction is an esterification reaction
condensation reaction
describe esterification reaction for large esters
heat under reflux and use fractional distillation to separate ester from other compounds
what is an acid anhydride ?
two carboxylic molecules - H20 (from condensation reaction)
how can ester be formed from acid anhydride and alcohol ?
react together with heat (no catalyst)
produces ester and carboxylic acid - separate with fractional distillation
what is the 3rd way to make an ester ?
alcohol + acyl chlorides, which forms and ester and HCl gas
what are the two ways to hydorlyse esters?
acid hydrolysis and base hydrolysis
what happens when you hydrolyse an ester ?
forms an alcohol
Describe acid hydrolysis of an ester
- splits ester into carboxylic acid and an alcohol
- heat under reflux with dilute acid (HCl)
- reversible reaction so lots of water needed
Describe base hydrolysis of an ester
- splits ester into carboxylate salt and alcohol
- heat under reflux with dilute alkali (NaOH)
why is kekule’s model no longer used?
the model suggested that there were C=C and C-C bonds with diff. lengths, when really they are all the same length
what 3D shape is benzene ?
planar (flat)
what are compounds containing a benzene ring called ?
arenes / aromatic compounds
electrons in benzene ring are …
delocalised
what evidence is there for benzene being more stable than kekule’s ?
hydrogenation is less exothermic than expected, so more energy needed to break bonds
what is thought to cause the stability of benzene ?
delocalised ring of electrons
what does a catalyst do to a species to allow it to act as an electrophile for benzene ?
polarises it
what type of reaction does benzene undergo ?
electrophillic substitution
what catalyst for chlorination of benzene ?
anhydrous AlCl3
what catalyst for bromination of benzene ?
anhydrous FeBr3
what catalyst / reagent for nitration of benzene ?
conc sulfuric acid, nitric acid
what conditions / reagents for alkylation of benzene ?
reflux, AlCl3 catalyst and haloalkane
what is the non organic product of nitration of benzene ?
water
what conditions / reagents for acylation of benzene ?
acyl chloride, reflux, AlCl3 catalyst
why keep temp lower than 55 for nitration of benzene ?
to get only one substitution
why is phenol more reactive than benzene ?
- lone pair on oxygen partially delocalises into electron ring
- increases electron density
- more likely to be attacked by electrophiles
what are some electron donating groups ?
OH-, NH2-
what positions for electron donating groups ?
2, 4, 6
what are some electron withdrawing groups ?
NO2+
what are the positions for electron withdrawing groups ?
3, 5
what is formed from reaction between bromine water and phenol ?
2,4,6-tribromophenol and hydrogen bromide
what is formed from the nitration of phenol ?
2 isomers of nitrophenol (at position 2 / 4)
water
what is needed for the nitration of phenol ?
just dilute nitric acid
what about phenol means it can undergo typical acid-base reactions ?
it is weakly acidic
what is the formula for acidified potassium dichromate ?
K2Cr2O7 / H2SO4
state the test for carboxylic acids
add sodium carbonate
effervescence shows positive test
what is the product formed from carboxylic acid test ?
carboxylate salt
what type of reaction is carboxylic acid test ?
acid - base
state the test for alkenes
add bromine water
orange colour decolourises
state the test for phenols
add bromine water
orange decolourises and white ppt forms
what type of reaction is test for phenol?
electrophillic substitution
state the test for aldehydes
add ammonical silver nitrate solution (tollens)
silver mirror will form
what product is formed in tollens ?
carboxylic acid
what type of reaction is tollens ?
oxidation
state the test for aldehydes and ketones
2,4-DNPH (Brady’s)
orange ppt will form from orange solution
what type of reaction is Brady’s ?
condensation
what reagent is used in the reduction of carbonyls ?
NaBH4
what type of mechanism is reduction of carbonyls ?
nucleophillic addition
what to remember with reduction of carbonyls ?
2 [H]
describe how hydrogen cyanide (HCN) reacts w/ carbonyls
dissociates to H+ and CN-
nucleophillic addition occurs w/ CN- as nucleophile
hydroxynitirle formed
what makes carboxylic acids so soluble ?
form H bonds with water
how do you name an acyl chloride ?
-oyl chloride
how are acyl chlorides formed ? (give products too)
carboxylic acid + SOCl2 — acyl chloride + SO2 + HCl
what substances do acyl chlorides react w/ and lose their chlorine ?
cold water / alcohol / ammonia / amine / phenol
when acyl chloride reacts and loses chlorine, what is ALWAYS formed ?
HCl gas
why are electron donating groups 2,4,6 directing ?
- electrons delocalise into ring, increasing electron density
- greater electron density at 2,4,6 carbons so more attracted to electrophiles
why are electron withdrawing groups 3,5 directing ?
- withdraws electrons from ring, decreasing electron density
- withdraws electron density from 2,4,6 so unlikely to react w/ these positions
