Organic Chem exam qs Flashcards
How to demonstrate ethene readily undergoes addition reaction with bromine water
- bubble/add ethene into bromine water (solution)
- brown bromine solution decolorised
would you expect benzene to readily undergo an addition reaction with bromine waer?
- no
- benzene is table/benzene has no double bonds/benzene bonds intermediate between double and single / benzene readily undergoes substitution
explain delocalised
-shared between more than two atoms / shared by more than one bonded pair of atoms / moving (not fixed) between one pair of bonded atoms and another
how many electrons in a benzene molecule are delocalised?
6
how many electrons in a benzene molecule are involved in sigma bonds between carbon atoms?
12
health hazard associated with benzene
carcinogenic
effect of adding tetraethyllead to an equimolar mixture of methane and chlorine exposed to weak sunlight
- reaction rate increases
- tetraethyllead acts as a catalyst / tetraethyllead provides ethyl free radicals
explain fractionation of crude oil
separation into components according to molecular size/by distillation
components of liquid petroleum gas
propane
butane
LPG
liquid petroleum gas
drawing propan-1-ol
draw a bond between the OH functional group when drawing molecules such as propan-1-ol just in case
why boiling pt of propanal is higher than that of butane
- propanal has dipole-dipole forces/propanal is polar/has a polar CO
- butane has weaker intermolecular forces/butane is non-polar
why boiling pt of ethanoic acid is higher than that of propan-1-ol
- ethanoic acid has stronger/more hydrogen bonding than propan-1-ol
- ethanoic acid has polar OH and CO bonds/has two polar groups
- propan-1-ol molecule only has a polar OH bond/one polar group
organic product of reaction of propanal with KMnO4
propanoic acid
spectroscopic technique that could help confirm identity of a sample of eugenol
IR spectrometry or spectroscopy
hydrocarbon gas produced by anaerobic bacterial decomposition of either animal waste or vegetation
methane
polymer of ethene
polyethene
how does the geometry around the carbon atoms change in the conversion of ethanol to ethene?
tetrahedral to planar
effect of presence of tetraethyllead in the conversion of ethane to chloroethane
incrases rate/speeds up reaction by providing ethyl free radicals
carbonyl group in an ester
it is the c and o (double bonded), does not count the single bond o
testing for aldehydes (2 methods)
- Mix Fehling’s 1 and 2
- Add to aldehyde and mix
- Heat gently
- Blue soln to red ppt is positive result
OR
- Add Tollen’s Reagent in clean test tube
- Add aldehyde, mix
- heat gently
- silver mirror is positive result
reactions of carboxylic acids
on table
test for unsaturation
Alkenes, alkynes decolourise bromine water
equation on table
safe disposal of sodium resides
on table
when naming alkenes
indicate where double bond is in IUPAC names
eg. 1-butene (bond on the end)
why catalytic cracking, dehydro etc are carried out
- inc octane number
- make more useful compounds
colour change as phenylmethanol is converted to benzoic acid, explain this colour change by reference to the transition metal used
purple to brown to colourless
MnO₄⁻ (Mn(IV)) changes to Mn²⁺ (Mn(II))
effect of adding tetraethyllead in conversion of alkane to chloroalkane
tetraethyllead increases rate by providing ethyl free radicals
“circle the carbonyl group in this ester”
circle both the C and the O (the double bonded one)
explain whether or not the kekule model correctly describes (i) the number, and (ii) the distribution
of pi electrons in benzene
(i) yes, each of the 3 double bonds has 2 pi electrons
(ii) electrons in benzene are delocalised
experimental evidence for delocalised electrons in benzene
All C-C bonds in benzene are of the same length, does not decolourise bromine water easily
bonds broken and formed on conversion of propanone to propan-2-ol
broken: pi bond of CO (carbonyl)
formed: OH, and CH
alkene intermolecular bonds
has Van der Waals forces between the molecules
alcohols intermolecular bonds
has hydrogen bonding between the molecules
ketones intermolecular bonds
has dipole-dipole forces between the molecules
“identify a carbon atom in planar geometry in this ester”
the carbonyl group will be the planar carbon
why propane has a lower bp than butane
propane: smaller Mr
therefore weaker intermolecular forces between molecules
homologous series
same functional group / similar chemical properties
how geometry is changed when ethene converted to ethane
mention bond angles, how it changes from bond angle of x to bond angle of y
why alkenes are more reactive than alkanes
- presence of double bond
- which can donate electrons /high electron density
identify alcohol propanone is converted to
propan-2-ol
its a secondary alcohol so make sure to specify instead of just writing “propanol”
why propanone doesnt react with fehling’s reagent even tho propanal does
propanone not oxidised easily
bonds broken and formed on conversion from ethanol to ethene
broken: C-H and C-O
formed: C=C and O-H
another organic compound besides ethanal that could be formed when ethanol is oxidised using acidified sodium dichromate
ethanoic acid
primary alcohol, cant be ketone? i guess?