Organic Synthesis

Question 1

what are the basics set of quickfit apparatus

Answer 1

round bottom or pear shaped flask
receiver
screw tap adapter
condenser
still head

Question 2

how can we heat organic reactions

Answer 2

it is common for reactions to be heated to overcome activation energy and increase rate of reaction.
Heating under reflux common procedure used to prepare an organic liquid without boiling of the solvent reactants or products

Question 3

what are apparatus needed to heat under relux

Answer 3

round bottom or pear shaped flask
condenser
rubber tubing
stand and clamp
heat source(usually a Bunsen burner, tripod and gauze or a heating mantle)

Question 4

why is a mantle used

Answer 4

for heating flammable liquids a heating mantle can be used so that there is no naked flame present
provides an added level of safety if any of the apparatus cracks or leak

Question 5

how to conduct reflux experiment

Answer 5

1)flask clamped by its neck. Before fitting in the condenser you need to add reaction mixture and anti-bumping granules to the flask
2)Finally apply a thin layer of grease to the ground glass joint of the condenser.
3)Place the condenser safely into the flask and gently rotate the condenser back and forth to provide a good seal and ensure that the apparatus comes apart easily at end of experiment

Question 6

why do you need add antibumping granules to the liquid before flask is heated

Answer 6

so contents boil smoothly. If not used large bubbles will form at the bottom of the liquid and make glassware vibrate and jump easily

Question 7

During reflux how should the condenser be positioned and clamped

Answer 7

up right
clamped loosely because glass outer jacket is very fragile and easily broken

Question 8

do we put a topper on the condenser

Answer 8

no you would have a closed system and pressure would build as heated air expands up causing the apparatus to explode.

Question 9

what is the rubber tubing used for in reflux

Answer 9

connect inlet of the condenser to the tap and outlet to the sink. Water enters condenser from the bottom and leaves from the top to ensure outer jacket is full

Question 10

What does heating under reflux enable liquid to do
and what does this prevent

Answer 10

to be continually boiled while reaction takes place
prevents volatile components from escaping and the flask from boiling dry.

Question 11

what is distillation

Answer 11

common method to seperate pure liquids from its impurities

Question 12

what apparatus needed for distillation

Answer 12

round bottom or pear shaped flask
condenser
rubber tubing
heat source
stand and clamp
screw-cap adapter
receiver adapter
still head
thermometer

Question 13

how to setup distillation

Answer 13

flask is clamped by its neck and still head connected to the flask. The still head adapter is T shaped and has two ground-glass joints, one to fit the screw-cap adapter and one to fit the condenser.
2)a second clamp placed round the receiver adaptor at the point at which it is attached to the condenser
.Thos removes the need to clamp the condenser as it will be supported efficiently at both ends
3)as with reflux the rubber tubing is used to connect the inlet of the condenser to tap and outlet to sink. Water always enters the condenser at the lowest point.
4)flask used to collect the distillate so that the distillation apparatus is not completely air tight.

Question 14

why should we grease the joints of the appparatus

Answer 14

so it comes of easily

Question 15

how to conduct distillation

Answer 15

Once apparatus setup the flaks is heated and mixture in flask will start to boil.The different liquids will have differnt boiling points. The liquid with the most boiling point is the most volatile and will boil first
2)The vapour moves out of the flask up into the other parts of the apparatus leaving behind the less volatile components of the mixture. When the vapours reach the cold condenser they condense and become liquid. This liquid then drips into condenser flask.

Question 16

how can you tell if you have to purify an organic layer

Answer 16

you will see two liquid layers inside your collection flask
one with organic layer and one with aqueous or water layer

Question 17

How to identify organic layer

Answer 17

add some water to your mixture . The layer that gets bigger is the aqueous solution

Question 18

How to purify organic products

Answer 18

1) ensure tap of the separating funnel is closed
2)Pour the mixture of liquids into separating funnel and place a stopper in the top of the funnel and invert to mix the contents
3)Allow the layers to settle
4)Add some water to see which layer increase in volume - this is the aqueous layer
5)Place a conical flask under the separating funnel remove the stopper and open the tap until whole of the lower layer has left the funnel.
6)Place second conical flask under separating funnel to collect the other layer
7)You will now have one conical flask containing organic layer and another containing aqueous layer. label flask

Question 19

how to remove acid impurities in impure product

Answer 19

adding aqueous sodium carbonate and shaking the mixture in the separating funnel
Any acid present will react with sodium carbonate and releasing carbon dioxide gas. The tap needed to be slowly opened, holding the stoppered separating funnel upside down to release any gas pressure that may build up
Finally the aqueous sodium carbonate layer is removed and the organic layer washed with water before running both layers off into two separate flasks

Question 20

What is a drying agent

Answer 20

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

Question 21

What are common drying agents

Answer 21

anhydrous chloride CaCl2 use drying hydrocarbons
anhydrous calcium sulfate CaSO4 General drying
anhydrous magnesium sulfate ,MgSO4 use for General drying

Question 22

Whats the procedure for drying an organic liquid

Answer 22

1)Add the organic liquid to a conical flask
2)Using a spatula, add some of the drying agentto the liquid and gently swirl the contents to mix together
3)Place stopper on the flask to prevent your product from evaporating away. Leave for about 10 minutes
4)If the solid has all stuck together in a lump, there is still some water present. Add more drying agent until some solid is dispersed in the solution as a fine powder
5)Decant the liquid from the solid into another flask. If the liquid is dry it should be clear

Question 23

why does redistillation occur

Answer 23

Sometimes organic liquids have boiling points that are relatively close together so your prepared sample may still contain some organic impurities

Question 24

what occurs in redistillation

Answer 24

distillation apparatus is cleaned and dried and set up again so that second distillation can be carried out. This time only collecting the product with the boiling point of the compound your trying to make. The narrower the boiling range the pure the product. You will now have separated your product from any impurities

Question 25

What are compounds used for as drying agents

Answer 25

Anhydrous calcium chloride drying hydrocarbon
Anhydrous calcium sulfate
Anhydrous magnesium sulfate

Question 26

Why does gas not leave in reflux reaction

Answer 26

The vapour from mixture rises up the inner tube of the condenser until it meets the outer jacket containing cold water.the vapour then condenses and drips back into flask

Question 27

What happens once apparatus set up in distillation

Answer 27

Flask heated and the mixture in the flask will start to boil.The different liquids in the mixture will have different boiling points. The liquid with the lowest boiling point is most volatile and boil first