16) Organic synthesis Flashcards

1
Q

Name 5 key quickfit apparatus that are often used in organic synthesis

A
round-bottom or pear-shaped flask
receiver
screw-tap adaptor
condenser
still head
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2
Q

Define reflux

A

the continual boiling and condensing of a reaction mixture back to the original container to ensure that the reaction takes place without the contents of the flask boiling dry

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3
Q

State 3 key things that heating under reflux helps to achieve

A

overcome activation energy
increase rate of reaction
prevent volatile components from escaping

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4
Q

Name 5 key apparatus used in a reflux

A
rubber tubing
Liebig condenser
clamp + stand
pear-shaped flask
heat source
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5
Q

In reflux, what should the direction of water flow ensure?

A

that the outer jacket of the condenser is full

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6
Q

In reflux, what is the rubber tubing connected to?

A

the inlet of the condenser

the outlet of a sink

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7
Q

Why should a Liebig condenser be clamped loosely?

A

very fragile

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8
Q

Why should a stopper not be placed on a Liebig condenser when undergoing reflux?

A

may explode

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9
Q

Why are the joints of some quickfit apparatus greased before use and then rotated back and forth when connecting to another piece of apparatus?

A

to ensure a good seal which comes apart easily after the experiment

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10
Q

What should be added to the reaction mixture in reflux to allow it to boil smoothly?

A

anti-bumping granules

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11
Q

What heat source without a naked flame could be used for reflux when heating flammable liquids?

A

a heating mantel

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12
Q

For reflux, should water go into a Liebig condenser at the top or the bottom?

A

at the bottom

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13
Q

Define distillation

A

common method to separate a pure liquid from its impurities (once reflux is complete)

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14
Q

Name 5 pieces of apparatus not used for reflux, that will be needed to carry out a distillation

A
thermometer
screw-cap adaptor / thermometer pocket
still head
receiver
conical flask
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15
Q

What is important about the use of a conical flask in a distillation?

A

means that the apparatus is not completely airtight

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16
Q

What property of a mixture of liquids is important for distillation to work? Why?

A

different boiling points
the liquid with the lowest boiling point is the most volatile and will boil first, when the vapours reach the condenser they will condense

17
Q

Describe the steps for purifying an organic product after distillation

A

1) ensuring separating funnel tap is closed, pour in mixture, place in stopper and invert to mix contents. allow to settle
2) identify aqueous layer (increases in volume when water is added)
3) place a conical flask under the separating funnel, remove the stopper and open the tap to allow the lower layer to be collected. repeat with a second conical flask for the other layer. label flasks

18
Q

What extra steps would be needed for the purification of an organic product if the preparation has used acids?

A

1) add aqueous sodium carbonate and shake the mixture in the separating funnel to remove an acid impurities
2) slowly open the tap whilst holding the funnel upside down to release any pressure as CO2 is produced
3) remove the aqueous carbonate layer and wash the organic layer with water

19
Q

Define drying agent

A

an anhydrous inorganic salt that readily takes up water to become hydrated

20
Q

Name a drying agent for drying hydrocarbons

A

anhydrous CaCl2

21
Q

Name 2 drying agents for general drying

A

anhydrous CaSO4

anhydrous MgSO4

22
Q

Give the 4 steps for drying an organic product

A

1) using a spatula, add drying agent to the organic layer in the conical flask and gently swirl to mix together
2) place on a stopper (prevent evaporation) and leave for 10 mins
3) If the solid has stuck together in a lump there is still water present - so add more drying agent until some solid is dispersed in the solution as a fine powder
4) decant the liquid from the solid into another flask. if the liquid is dry it should be clear

23
Q

Why would you dry an organic product?

A

to remove traces of water

24
Q

When carrying out a second distillation what change would you make?

A

collect only the product with the boiling point of the compound you are trying to make

25
Q

The _ the boiling range, the purer the product.

A

narrower

26
Q

Define organic synthesis

A

the preparation of complex molecules from simple starting materials

27
Q

haloalkane -> alcohol

A

NaOH(aq)

reflux

28
Q

alkane -> haloalkane

A

halogen/UV

29
Q

alkene -> haloalkane

A

hydrogen halide

30
Q

alkene -> alcohol

A

H2O(g)

H3PO4 catalyst

31
Q

alkene -> alkane

A

H2

Ni catalyst

32
Q

alcohol -> haloalkane

A

sodium halide + H2SO4

33
Q

alcohol -> alkene

A

conc. H2SO4

34
Q

primary alcohol -> carboxylic acid

A

K2Cr2O7/H2SO4 reflux

35
Q

primary alcohol -> aldehyde

A

K2Cr2O7/H2SO4 distil

36
Q

secondary alcohol -> ketone

A

K2Cr2O7/H2SO4 reflux

37
Q

Define target molecule

A

the compound the chemist is attempting to prepare by organic synthesis

38
Q

Describe how you would prepare to carry out a two-step synthesis

A

identify functional groups in starting and target molecules
identify the intermediate
state reagents and conditions for each step