Organic stuff wrong from mock Flashcards
name 2 electron donating and 1 electron withdrawing groups + what they do
EDG: OH, NH2. Directs electrophilic substitution towards 2-,4- and 6- positions. EWG: NO2. Directs electrophilic substitution towards 3- and 5- positions.
write a balanced equation for the oxidation of 3-methylbutan-1,2,3-triol
draw the equation for alkali hydrolysis of methanoic acid with NaOH (display formula)
whats bonds can alkali hydrolysis break
- esters (quickly)
- amides (slowly)
why is phenol more readily attacked by electrophiles than benzene
- OH group is electron donating
- lone pair in p-orbital of oxygen atom overlaps with delocalised ring
- lone pair partially delocalised into π-system
- increases electron density of benzene ring
- allows phenol to polarise/attack NO2+ electrophile more readily than benzene
what effects the rate of hydrolysis of haloalkanes
bond enthalpy
whats the trend of C-X bond enthalpy as you go down group 7
bond enthalpy of C-X decreases as you go down the group, increasing the rate of hydrolysis
whats the general equation for the hydrolysis of haloalkanes with aqueous alkali
RX + OH- -> ROH + X-
draw the machanism for chlorocyclohexane hydrolysed by aqueous sodium hydroxide
what practical technique should be used for carrying out hydrolysis of a haloalkane
reflux
draw reflux apparatus
draw distillation apparatus
draw filtration apparatus
How would you use the products of a chemical test such as Bradys to identify a compound
- precipitate formed from test can be used to measure melting point with melting point apparus
- values can be compared to know data values
draw the mechanism for electrophillic addition of bromine onto ethene
draw 1°,2° and 3° carbocations and state their relative stabilities
explain markowinikoffs rules
- if hydrogen halide adds to an unsymetrical alkene theres two posible products.
- amount of product formed depends on how stable the carbocatios formed in the middle of the reaction
- carbocations with more alkyle groups= more stable because they feed electrons towards the positive charge(shown by arrows on bonds)
- more stable cations likely to form than less stable ones, first step of mechanism more likely to lead to the frmation of the most stable carbocation
- major product = via more stable carbocation
draw the product of salicyclic acid + Na2CO3 (aq)
draw the prouduct of salicyclic aid + NaOH (aq)
write the equations for the complete+incomplete combustion of methanol
compare intermolecular forces
compare the boiling points of alkanes and alcohols
- alcohols higher as -OH group forms H bonds with other alcohol molecules(and water), this is strongest intermolecular force so bp higher
- alakanes only form london forces between molecules(weaker than H bonds). Longer carbon chain ->larger molecular surface area -> more surfaece area contact bewtween molecules + more elctrons -> more london forces, more energy to overcome, higher bp
define homologous series
a family of organic compounds that have the same general formula and similar chemical properties
whats the general formula of alcohols
CnH2n+2O
- what happens to bond enthalpy of X-C as you go down group 7
- what does this affect
- C-X bond enthalpy decreases, C-F strongest, C-I weakest
- rate of hydrolysis/nucleophilic substitution
whats affects Rf values
level of adosrbtion, a substance thats strongly adsorbed wont travel as far giving it a smaller value. chemical properties such as polarity affect how strongly adsorbed a substance is. Also depends on solid coating on the plate, solvent used, and other external factors e.g. temp.
name 3 ways of disposing of non-biodegradable polymers
- burying in landfill
- recycling plstics, sorted into group, some melted and remoulded, other cracked into monomers used as organic feedstock
- burning plastic waste, is recycling isnt possible, heat used to generate electricity, produces toxic gasses e.g. HCl. removed by scrubbers that neutralise
halide test
plus further test
- dissolve in distilled water
- add dilute nitric acid (HNO3)
- add silver nitrate(AgNO3)
- silver halide precipitate forms
obs: cl=white
Br= cream
I= yellow
If still indistinguishable furher ammonia test
- add dilte NH3, look for prcpt dislloving
- add conc ammonia
obs: cl- = dissolves in dilute ammonia
Br- = only dissolves in conc ammonia
I- = deosnt dissolve
what order do you do test to prevent false positive
carbonates->sulfates->halides
describe the test for carbonates->sulphates->halides
carbonates: -add diltue strong acid(HNO3)
obs: CO2 relased, limewater
sulphates: -add barium nitrate, Ba(NO3)2(aq)
obs: white prcpt forms
halides: -add nitric acid, then silver nitrate
obs: prcpt forms, cl=white, br=cream, i=yellow
test for ammonim ons
- add NaOH(aq)
- warm
- hold damp litmus paper over top of test tube
obs: paper turns blue
test for unsaturated
- add Br2
obs: decolourised Br2
test for 1°/2° alcohols
- oxidise with k2cr2o7
obs: orange to green
test for aldehydes
- add tollens
- place in warm water bath
obs: silver mirror forms
test for carbonyls
- add bradys reagents
- shake
obs: bright orange precipitate
test for phenol
1) -add NaOH
obs: fizzes, colourless solution of sodium salt would form
2) -add Na2CO3(s)
obs: nothing happens
test for carboxylic acids
-add Na2CO3
Obs: solution fizzes, CO2 released, bubble through lime water
atom economy formula
(Mr of desired product/sum of Mr’s of products) X100
draw mirror images of optical isomers of amino acid with R=CH
How does GC-MS work
- sample is injected and vapourised
- stream of carrier gas carries the sample through a coiled tube coated with a viscous liquid or a solid
- time taken for substance to pass through coiled tube and reach detector = retnetion time
how do you work out the % in orginal mixture of a compound from a ags chromatogram
area of peak/total area of all peaks
whats the difference between gas chromatography with liquid and solid coatings
- in liquid the components will constantly dissolve in it, evaporate into gas, and then redissolve as they travel through the tube. Solubility determines retention time. High solubility = more time dissolved, so longer to travel through detector than one with lower solubility
- in solid, strength of adsorbtion to solid determines retention times.
what 3 factors effect retention times
1) solubility/adsorbtion, determines how long each component of the mixture spends in the stationary phase
2) boiling point, substance with high boiling points will spend more time condensed as a liquid in the tube than a gas. larger retention time
3) temperature og GC, high temp = more time evaporated as gas so will move along faster, shortens retention time
what does creating an external calibration curve from GC allow you to do
-calculate the concentration of a particular substance
4 steps to mkaing calibration curve
1) create series of standard solutions of different concentrations of analyte
2) one by one, inject all standard solutions recording results
3) calculate area under the peak that corresponds to the analyte
4) plot these area value on a graph of area against concentration, draw line of best fit
its a good idea to run a blank when making calibration curve. subtracting chromatogram of blank from each of chromatograms you can find correct peak value.
how are acid anhydrides produced
2 identical carboxylic acids molecules join together via and oxygen with the carbonyl groups on either sides.
acid anhydride + alcohol ->
Ester + carboxylic acid
formation of nitronium ion, electrophile
HNO3 + H2SO4 -> HSO4- + NO2+ + H2O
formation of HCN from NaCN and H2SO4
2NaCN + H2SO4 -> 2HCN + Na2SO4
what are the bond angles in a tetrahedral molecule
109.5°
why is raical substitution bad at making a single substance
- multiple determination steps
- further substitution
- substitution at anywhere on the c chain
explain ozone depletion
- ozone levels stable until recently due to dynamic equillibrium in stratosphere
- CFC’s lead to ozone depletion
- stable(high bond enthalpy) so not broken down in atmosphere
- broken down by UV radiation in stratosphere
what radicals destroy ozone other than Cl
NO free radical
from nitrogen oxides from vehicle engines and thunderstorms
what are the substitutes for CFC’s
HCFC and HFC
what are the main greenhouse gasses,
why
-what factors determine how much a gas contributes
water vapour, CO2, methane,
bonds absorb infrared->vibrate->kinetic energy->raising overall temp
- how much IR absorbed per molecule,
- how much gas in atmosphere
- how long gas stays in atmosphere
whats global warming
rise is greenhouse gas concentrations, enhancing greenhouse gas effect. more heat trapped heating earth
how do you ensure prduction of 1° amine
excess ammonia
avoids further substitution to 2°/3°
