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OCR A Chemistry > organic synthesis > Flashcards

organic synthesis Flashcards

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1
Q

Alkane —-> haloalkane

conditions, type of reaction & equations

A

conditions: type of reaction:
x2/UV light radical substitution

INITIATION: homolytic fisson

x2 ———> 2x •

PROPAGATION:
1: CH4 + Br • ——> CH3• + HBr

2: CH3• + Br2 ——> CH3Br + Br•

TERMINATION:

2Br• ——> Br2

2CH3• ——> C2H6

CH3• + Br • ——> CH3Br

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2
Q

Limitations of free rad substitution

A

FURTHER SUBSTITUTION
- another radical can collide with the final molecule

  • substituting another alkane
  • further sub can happen until ALL H has been subbed

SUBSTITUTION AT DIFFERENT POINTS IN A CARBON CHAIN
- for longer carbon chains, halogens can substitute on diff places on the chain

—-> resulting in diff compounds being formed

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3
Q

alkene to alkane

A

hydrogenation/addition reaction

H2/ Ni catalyst

423K

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4
Q

alkene to haloalkane

A

hydrogen halide or halogen
eg : Hbr or Br2

ELECTROPHILIC ADDITION

with Hbr or Br2
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5
Q

alkene to alcohol

A

H20 (g)/ acid catalyst (H3PO4)

  • two products
  • alcohol can go on either side of cc double bond
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6
Q

haloalkalkane to alcohol

A

NaOH(aq)

NUCLEOPHILIC SUBSTITUTION

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7
Q

Alcohol to haloalkane

A

hydrogen halide MADE IN SITU

NaBr + H2SO4 ——-> HBr + NaHSO4

ch3oh + HBr ——-> ch3br + h20

OVERALL EQUATION
ch3oh + NaBr + h2so4 ——-> ch3br + nahso4 + h20

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8
Q

Haloalkane to nitrile

A

NaCN(aq)

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9
Q

Haloalkane to straight chain AMINE

A

excess NH3/ethanol

ethanol as solvent —-> prevents sub of haloalkane by water to alcohol

excess NH3 ——> reduces further sub if amine group to form 2* & 3* amins

NUCLEOPHILIC SUB

CH3CH2Br + NH3 ——> CH3CH2NH3+Br-

CH3CH2NH3+Br- + NaOH —-> CH3CH2NH2 + NaBr + H20

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10
Q

forming 2* & 3* aliphatic amines

A

FURTHER SUBSTITUTION
forming 2* and 3* amines

CH3CH2Cl + CH2CH2NH2 ——> (CH3CH2CH2)2NH2+Cl-

(CH3CH2CH2)2NH2+Cl- + NaOH ——-> (CH3CH2CH2)2NH + NaCl + H2O

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11
Q

1* alcohol to aldehyde

A

acidified Cr207- / H2SO4/H+

distil

CH3CH2OH + [o] ——-> ch3cho +h20

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12
Q

1* alcohol to carboxylic acid

A

acidified cr2o7 2- / excess h2so4

REFLUX

ch3ch2oh +2[o] ——> ch3cooh +h20

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13
Q

2* alcohol to ketone

A

acidified cr2o7 2- /h2so4

REFLUX

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14
Q

oxidation of 3* alcohol

A

NO REACTION

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15
Q

alcohol to alkene

A

DEHYDRATION

acid catalyst
h2so4 or conc h3po4

REFLUX

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16
Q

alcohol to ester

A

carboxylic acid/ conc h2so4
warmed

acyl chloride
acid anhydride

17
Q

aldehyde to hydroxynitrile

A

NaCN/H+

NUCLEOPHILIC ADDITION

18
Q

aldehyde to alcohol

A

REDUCTION
NUCLEOPHILIC ADDITION

NaBH4/ H2O (H-)
warmed

19
Q

carboxylic acid to acyl chloride

A

SOCl2

socl2 —-> so2(g) + hcl

20
Q

carboxylic acid to ester

A

alcohol / conc h2so4

21
Q

Acyl chloride to ester

A

alcohol

or

OR

phenol
- carb acids are too unreactive to form esters with phenol

22
Q

acyl chloride to carboxylic acid

A

h20

produces HCl (g)

23
Q

acyl chloride to 1* amiDe

A

2NH3

24
Q

acyl chloride to 2* amiDe

A

react with 1* amiNe

25
Q

reactions of acid anyhydrides

A

react in similar way to acyl chlorides

-react with:
phenols
water
amines
ammonia
26
Q

ester to carb. acid + alcohol

A

HYDROLYSIS

acid hydrolysis

  • H+/H2O
  • reflux

alkaline hydrolysis (saponification)

  • NaOH/H2O
  • reflux
  • irreversable

forms a salt and alcohol

27
Q

Nitrile to carboxylic acid

A

Hydrolysis

H2O/ HCl

28
Q

nitrile to amiNe

A

H2/Ni

29
Q

benzene to nitrobenzene

A

electrophilic addition
HNO3/H2SO4

nitronium ion, NO2+ electrophile
HNO3 + H2SO4 ——> NO2+ + HSO4- +H20

FOR SINGLE SUBSTITUTION
50 °C

FOR TWO SUBS - 1,3-dinitrobenzene
70 °C
excess ammonia

30
Q

halogenation of benzene

A

NEED HALOGEN CARRIER - AlCl₃ , FeBr₃

halogen

Br₂ + FeBr₃ —-> FeBr₄- + Br+

                      FeBr₃ benzene + Br₂ ——> bromobenzene + Hbr
31
Q

adding acyl group onto benzene

A

HALOGEN CARRIER/ETHANOYL CHLORIDE

ALCl₃/CH₃COCl

phenylethanone + HCl

32
Q

filtration under reduced pressure method

A

Buchner flask

Buchner funnel

pressure tubing

filter paper

access to filter or vacuum pump.

  1. Connect one end of the pressure tubing to the vacuum outlet or to the filter pump whilst attaching the other end of the rubber tubing
    to the Buchner flask.

2.Fit the Buchner funnel to the Buchner flask ensuring that there is
a good tight fit. This is usually obtained using a Buchner ring or a
rubber bung

3.Switch on the vacuum pump, or the tap, to which your filter
pump is attached.
4.Check for good suction by placing your hand across the top of the
funnel.

5.Place a piece of filter paper inside the Buchner funnel and wet this
with the same solvent used in preparing your solid. You should see
the paper being sucked down against the holes in the funnel.

6.To filter your sample, slowly pour the reaction mixture from a
beaker into the centre of the filter paper.

7.Rinse out the beaker with the solvent so that all of the solid
crystals collect in the Buchner funnel.

8.Rinse the crystals in the Buchner funnel with more solvent and
leave them under suction for a few minutes so that the crystals start to dry

33
Q

RECRYSTALLISATION METHOD

A

Recrystallisation

The solid product obtained after filtration will contain impurities
which can be removed by carrying out recrystallisation. Purification by
recrystallisation depends upon the desired product and the impurities
having different solubilities in the chosen solvent.

1
Pour a quantity of the chosen solvent into a conical flask. If the
solvent is flammable, warm the solvent over a water bath. If the
solvent is water, place the conical flask on a tripod and gauze over
a Bunsen and warm the solvent.

2
Tip the impure sample into a second conical flask or beaker.

3
Slowly add the solvent to the impure sample until it dissolves
in the solvent. You should add the minimum volume of solvent
needed to dissolve the solid.

4 Once the solid has dissolved, allow the solution to cool. Crystals of
the desired product should form in the conical flask or beaker
When no more crystals form, filter the crystals under reduced pressure to obtain the dry crystalline solid

OCR A Chemistry (6 decks)

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