Organic Chem exam qs Flashcards Preview

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Flashcards in Organic Chem exam qs Deck (44)
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1
Q

How to demonstrate ethene readily undergoes addition reaction with bromine water

A
  • bubble/add ethene into bromine water (solution)

- brown bromine solution decolorised

2
Q

would you expect benzene to readily undergo an addition reaction with bromine waer?

A
  • no
  • benzene is table/benzene has no double bonds/benzene bonds intermediate between double and single / benzene readily undergoes substitution
3
Q

explain delocalised

A

-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

4
Q

how many electrons in a benzene molecule are delocalised?

A

6

5
Q

how many electrons in a benzene molecule are involved in sigma bonds between carbon atoms?

A

12

6
Q

health hazard associated with benzene

A

carcinogenic

7
Q

effect of adding tetraethyllead to an equimolar mixture of methane and chlorine exposed to weak sunlight

A
  • reaction rate increases

- tetraethyllead acts as a catalyst / tetraethyllead provides ethyl free radicals

8
Q

explain fractionation of crude oil

A

separation into components according to molecular size/by distillation

9
Q

components of liquid petroleum gas

A

propane

butane

10
Q

LPG

A

liquid petroleum gas

11
Q

drawing propan-1-ol

A

draw a bond between the OH functional group when drawing molecules such as propan-1-ol just in case

12
Q

why boiling pt of propanal is higher than that of butane

A
  • propanal has dipole-dipole forces/propanal is polar/has a polar CO
  • butane has weaker intermolecular forces/butane is non-polar
13
Q

why boiling pt of ethanoic acid is higher than that of propan-1-ol

A
  • 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
14
Q

organic product of reaction of propanal with KMnO4

A

propanoic acid

15
Q

spectroscopic technique that could help confirm identity of a sample of eugenol

A

IR spectrometry or spectroscopy

16
Q

hydrocarbon gas produced by anaerobic bacterial decomposition of either animal waste or vegetation

A

methane

17
Q

polymer of ethene

A

polyethene

18
Q

how does the geometry around the carbon atoms change in the conversion of ethanol to ethene?

A

tetrahedral to planar

19
Q

effect of presence of tetraethyllead in the conversion of ethane to chloroethane

A

incrases rate/speeds up reaction by providing ethyl free radicals

20
Q

carbonyl group in an ester

A

it is the c and o (double bonded), does not count the single bond o

21
Q

testing for aldehydes (2 methods)

A
  • 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
22
Q

reactions of carboxylic acids

A

on table

23
Q

test for unsaturation

A

Alkenes, alkynes decolourise bromine water

equation on table

24
Q

safe disposal of sodium resides

A

on table

25
Q

when naming alkenes

A

indicate where double bond is in IUPAC names

eg. 1-butene (bond on the end)

26
Q

why catalytic cracking, dehydro etc are carried out

A
  • inc octane number

- make more useful compounds

27
Q

colour change as phenylmethanol is converted to benzoic acid, explain this colour change by reference to the transition metal used

A

purple to brown to colourless

MnO₄⁻ (Mn(IV)) changes to Mn²⁺ (Mn(II))

28
Q

effect of adding tetraethyllead in conversion of alkane to chloroalkane

A

tetraethyllead increases rate by providing ethyl free radicals

29
Q

“circle the carbonyl group in this ester”

A

circle both the C and the O (the double bonded one)

30
Q

explain whether or not the kekule model correctly describes (i) the number, and (ii) the distribution
of pi electrons in benzene

A

(i) yes, each of the 3 double bonds has 2 pi electrons

(ii) electrons in benzene are delocalised

31
Q

experimental evidence for delocalised electrons in benzene

A

All C-C bonds in benzene are of the same length, does not decolourise bromine water easily

32
Q

bonds broken and formed on conversion of propanone to propan-2-ol

A

broken: pi bond of CO (carbonyl)
formed: OH, and CH

33
Q

alkene intermolecular bonds

A

has Van der Waals forces between the molecules

34
Q

alcohols intermolecular bonds

A

has hydrogen bonding between the molecules

35
Q

ketones intermolecular bonds

A

has dipole-dipole forces between the molecules

36
Q

“identify a carbon atom in planar geometry in this ester”

A

the carbonyl group will be the planar carbon

37
Q

why propane has a lower bp than butane

A

propane: smaller Mr

therefore weaker intermolecular forces between molecules

38
Q

homologous series

A

same functional group / similar chemical properties

39
Q

how geometry is changed when ethene converted to ethane

A

mention bond angles, how it changes from bond angle of x to bond angle of y

40
Q

why alkenes are more reactive than alkanes

A
  • presence of double bond

- which can donate electrons /high electron density

41
Q

identify alcohol propanone is converted to

A

propan-2-ol

its a secondary alcohol so make sure to specify instead of just writing “propanol”

42
Q

why propanone doesnt react with fehling’s reagent even tho propanal does

A

propanone not oxidised easily

43
Q

bonds broken and formed on conversion from ethanol to ethene

A

broken: C-H and C-O
formed: C=C and O-H

44
Q

another organic compound besides ethanal that could be formed when ethanol is oxidised using acidified sodium dichromate

A

ethanoic acid

primary alcohol, cant be ketone? i guess?