Organic Synthesis and Analytical Techniques (IR and MS)

Question 1

Why do we need the ozone layer?

Answer 1

It helps to filter out harmful ultraviolet radiation. Overexposure to UV can cause skin cancers, cataracts, and damage to crops

Question 2

Why do we heat under reflux?

Answer 2

Heating under reflux is vaporisation followed by condensation back to the original container. Under reflux, reactants can be heated safely for a long period of time without the reaction mixture boiling dry.

Question 3

What is distillation?

Answer 3

Distillation is used to separate a liquid from a solution or form a mixture of liquids. Distillation is vaporisation followed by condensation to a different container. It can be used to purify a liquid product by removing unreacted reagents and unwanted by-products. Different liquid components can be separated by collection at diff BPs

Question 4

How do you remove impurities from organic liquids?

Answer 4

If the liquid and water are immiscible then the two layers are separated by adding the mixture to a separating funnel and carefully running off each layer. Acid impurities can be removed by adding a solution of sodium carbonate. An organic layer can then be separated from the aqueous sodium carbonate layer using a separating funnel.

Question 5

How do you dry an organic product (after removing impurities)?

Answer 5

Any water left after using a separating funnel then it is removed using a drying agent such as an anhydrous salt e.g. magnesium sulfate or anhydrous calcium chloride

Question 6

Why would you redistill an organic product?

Answer 6

If two organic liquids have very similar boiling points, it may be necessary to distil the product a second time to ensure that only the pure liquid is collected.

Question 7

How do you form haloalkanes from alkanes?

Answer 7

React an alkane with a halogen in the presence of UV light

Question 8

How do you form alkanes from alkenes?

Answer 8

React the alkene with H2 in the presence of a nickel catalyst

Question 9

How do you form haloalkanes from alkenes?

Answer 9

React the alkene with a halogen/hydrogen halide

Question 10

how do you form alcohols from alkenes?

Answer 10

React the alkene with H2O in the presence of a phosphoric acid catalyst

Question 11

How do you form poly(alkanes) from alkenes?

Answer 11

Addition polymerisation

Question 12

How do you form alkenes from alcohols?

Answer 12

Dehydration using hot concentrated sulfuric acid

Question 13

How do you form haloalkanes from alcohols?

Answer 13

React the alcohol with a sodium halide in the presence of sulfuric acid

Question 14

How do you form alcohols from haloalkanes?

Answer 14

React the haloalkane with aqueous sodium hydroxide

Question 15

Absorption of infrared radiation by atmospheric gases

Answer 15

The covalent bonds in molecules naturally vibrate however vibrate more in the presence of IR. Infrared radiation is mainly absorbed by gases containing C=O, O-H and C-H bonds and re-radiated as heat energy

Question 16

Application of IR spectroscopy in environmental chemistry

Answer 16

Monitoring of gases that cause air pollution e.g. CO and NO from car emissions-In breathalysers to measure ethanol in the breath