Organic synthesis and Spectroscopy

Question 1

What does heating under reflux do ?

Answer 1

• enables a liquid to be continually boiled whilst the reaction takes place, which prevents any of the reaction mixture from escaping

Question 2

What labels are needed for a diagram of heat under reflux ?

Answer 2

• heat
• flask
• condensor
• water in
• water out

Question 3

What is distillation used for ?

Answer 3

• separates a pure liquid from its impurities
• heats a reaction mixture and immediately separates a pure liquid from the rest of the mixture

Question 4

What labels are needed for a diagram of heat under distillation ?

Answer 4

• heat
• flask
• condensor
• water in
• water out
• beaker

Question 5

What labels are needed for a diagram of a separating funnel ?

Answer 5

• beaker
• separating funnel

Question 6

Describe how you would separate the organic liquid 1-bromobutane from a mixture of 1-bromobutane, water and sulfuric acid.

Answer 6

• pour the mixture into a separating funnel
• add sodium carbonate solution and shake, releasing the gas pressure
• separate the aqueous layer, then add distilled water to the organic layer in the separating funnel and shake again
• separate the layers
• add a drying agent to dry
• filter off the drying agent

Question 7

What happens when molecules absorb infrared radiation ?

Answer 7

the covalent bonds in the molecule vibrate

Question 8

What does the amount that bond stretches or bends depend on ?

Answer 8

• the strength of the bond
• the mass of the bond

Question 9

What are the frequencies of infrared absorbed by the bonds measured using ?

Answer 9

wavenumber in cm^-1

Question 10

What are the 3 main greenhouse gases that absorb infrared radiation in the atmosphere ?

Answer 10

• CO2 (carbon dioxide)
• CH4 (methane)
• H2O (water vapour)

Question 11

How do greenhouse gases aid in global warming ?

Answer 11

• they absorb infrared radiation re-emitted from the Earth and the vibrating bonds re-emit the radiation
• this increases the temperature of the atmosphere, leading to global warming

Question 12

What are the uses of infrared spectroscopy ?

Answer 12

• remote sensors for analysis of vehicle emissions
• in breathalysers to detect ethanol

Question 13

What is a molecular ion (M+) ?

Answer 13

the positive ion formed when a molecule loses and electron in the mass spectrometer

Question 14

Which peak is the molecular ion peak on a mass spectrum ?

Answer 14

the peak that is furthest to the right

Question 15

What do some molecular ions break down into ?

Answer 15

positive fragment ions and neutral radicals