organic chem and analysis Flashcards
why was kekules model incorrect
benzene doesn’t decolourise bromine water
has a much less exothermic enthalpy change of hydrogenation than expected
what are the conditions for nitration of benzene?
50ºC
concentrated acids
conc H2SO4 catalyst
what are examples of a halogen carrier catalyst?
AlCl3
FeCl3
AlBr3
FeBr3
What are examples of election donating groups?
OH
NH2
CH3
What do election donating groups do?
Donate electron density into the pi system
Make it more reactive
Activate electrophile attack
Direct incoming electrophile to Carbon 2 and 4
What is an example of an electron withdrawing group?
NO2
What do election withdrawing groups do?
Remove electron density from the pi system
Make it less reactive
Deactivate electrophile attack
Direct incoming electrophiles to carbon 3
What is carbon position 2/6 called
Ortho
What is carbon position 3/5 called
Meta
What is carbon position 4 called?
Para
what are examples of stationary phase in TLC?
silica
alumina
What is the stationary phase in gas chromatography?
Long coiled column, usually a non volatile liquid
What is the mobile phase in gas chromatography?
Inert carrier gas
Eg helium, nitrogen
what is the test for alkenes?
shake w orange bromine water
addition reaction takes place
decolourises bromine water
what is the test for haloalkanes?
warm the haloalkane with NaOH in a mixture of ethanol and water
haloalkane will undergo nucleophilic substitution and release the halide ion into solution
acidify sample of halide ion w dilute nitric acid to remove carbonate ions
add silver nitrate
forms silver halide ppt
AgCl - white
AgBr - cream
AgI - yellow
what is the test for alcohols?
1cm3 of alcohol in test tube
1cm3 of acidified potassium dichromate (oxidising agent)
add stopper to test tube and shake
place in 60ºC water bath for few mins
primary/ secondary= orange to green
tertiary= stays orange
what is the test for carboxylic acids?
pH probe or dip end of glass rod in solution then on indicator paper- pH3
OR
1-2cm3 sodium carbonate added
gas bubbled produced
gas bulbbled into limewater
limewater turns cloudy
confirming gas is CO2
what is the test for phenols?
shaken w bromine water
substitution reaction
decolourises bromine water
white ppt forms
what are samples measured against in NMR and why?
TMS
produces single intense peak at far rhs
protons highly shielded
inert
non toxic
what are the components of a NMR spectrometer?
radio wave source
radio wave detector
stable magnetic field formed by superconducting coils and elecrtomagnets
which type of atoms need more energy to resonate in NMR?
more deshielded
what are samples for NMR analysis dissolved in and why is this used?
deuterated solvents
all 1H replaced by deuterium D 2H
produces no signals in NMR
in proton NMR, what does the ratio of the relevant areas under each peak represent?
ratio of how many protons responsible for each peak
in proton NMR, how is the number of adjacent protons represented?
number of adjacent protons + 1
= number of sub peaks
what can be used to test for carbonyl compounds
2,4- DNP
what forms when 2,4- DNP is added to a carbonyl compound
orange ppt
which can be used to identify specific carbonyl:
recrystallise
measure mp of ppt
compare against known values
what can be used to test for aldehydes?
Tollen’s reagent
how to make Tollens reagent
add aqueous ammonia to a solution of silver nitrate
what happens when an aldehyde is gently warmed w Tollen’s regent
aldehyde oxidised to carboxylic acid
colourless silver ions reduced to solid silver metal
forms a silver mirror
what forms when a primary alcohol is distilled with an oxidising agent
aldehyde
what forms when a primary alcohol is refluxed with an oxidising agent
carboxylic acid
what forms when an aldehyde is distilled with an oxidising agent
carboxylic acid
what oxidising agent is used
acidified potassium dichromate
K2Cr2O7 with H2SO4
what is the colour change when acidified potassium dichromate oxidises
orange to green
can ketones be further oxidised
no
no readily available H
strong oxidising agent wld be needed
wld likely oxidise in a destructive way
breaking a C-C bond
What type of reactions do carbonyls undergo
Nucleophilic addition
During the addition of HCN to carbonyls, where can H+ ions come from
HCN
Water
Dilute acid
When HCN is added to carbonyls, what is formed
Hydroxynitrile
What is the priority group in hydroxynitriles
Nitrile
How are hydroxynitriles named
Nitrile suffix
Hydroxy prefix
What can aldehydes be reduced into
Primary alcohol
What can ketones be reduced into
Secondary alc
What is the most common reducing agent for carbonyls
NaBH4
What is a nucleophile
An atom or group of atoms that is attracted to an area of electron deficiency where it donates an electron pair
What is a negative hydrogen ion called
Hydride ion
What is the nucleophile from HCN
CN-
Where is the lone pair on CN-
Carbon
What is used to provide hydrogen cyanide (HCN)
Sodium cyanide
Sulphuric acid
Hydrogen cyanide (HCN) properties
Colourless
Poisonous
Liquid
Boils slightly above room temp
which carboxylic acids are soluble
up to 6 C
are carboxylic acids strong or weak acids and why
weak
partially ionises
equilibrium lies to the left
what do carboxylic acids dissociate into
carboxylate ion
proton
dicarboxylic acids state at room temp
solid
do dicarboxylic acids dissolve readily in water
yes
test for carboxylic acids
add carbonate
effervescence
carboxylic acid + alkali
salt + water
carboxylic acid + metal oxide
metal salt + water
carboxylic acid + carbonate
salt + water + carbon dioxide
what is a carboxylic acid derivative
compound that can be hydrolysed to form the parent carboxylic acid
all have an acyl group
what is the ester functional group
COO
how do esters smell
sweet
fruity
how are esters formed with a carboxylic acid and an alcohol
condensation reaction
conc sulphuric acid catalyst
heat under reflux
reversible reaction
low yield
how are esters formed with an acid anhydride and an alcohol
room temp
no catalyst
not reversible reaction
higher yield
which is more reactive: acid anhydride or carboxylic acid
acid anhydride
what happens when esters are heated under reflux with dilute acid
reversible reaction
carboxylic acid and alcohol produced
what happens when esters are heated under reflux with dilute alkali
irreversible reaction
forms alcohol and carboxylate salt
which needs further acidification
to make carboxylic acid
acyl chloride functional group
COCl
how are acyl chlorides formed
carboxylic acid
and
liquid sulfur dichloride oxide (SOCl2)
forms
acyl chloride, HCl, SO2
what type of reactions can acyl chlorides undergo
addition elimination
what does hydrolysis of acyl chlorides form
carboxylic acid
HCl
why is hydrolysis of acyl chlorides an addition- elimination reaction
H2O added across C=O
HCl eliminated
what can acyl chlorides react with to form esters
alcohols or phenols
what is required to form an ester from an acyl chloride and a phenol
heat
a base eg NaOH
what does the reaction of an acyl chloride and ammonia form
primary amide
what does the reaction of an acyl chloride and a primary amine form
secondary amide
metal carbonate state at room temp
solid
