Chapter 5 - Whats In Medicine

Question 1

how to prepare asprin

Answer 1

use an acylation reaction to make the ester bond and to form asprin using a powerful acylating agent

Question 2

describe the procedure for recrystallisation

Answer 2

• dissovle in a minimum volume
• of hot solvent
• in which the material is soluble at high temperatures but insoluble at low temperatures
• hot filtration to remove insoluble impurities
• allow to cool and crystalise
• vacuum filter the crystals, wash with cold solvent and allow to dry

Question 3

what does heating under reflux do

Answer 3

enables a mixture including volatile substances to be heated for a long time without loss of solvent

Question 4

describe the process of vacuum filtration

Answer 4

• connect a conical ‘buchner’ flask to the vacuum pump
• dampen a piece of filter paper and place it flat on the buchner funnel
• turn on the vacuum, air pressure will push the solvent through the paper due to the partial vacuum in the flask

Question 5

describe how to carry out thin-layer chromatography

Answer 5

• spot small sample of mixture on base pencil line
• spot of reference substance at same level on line
• on sheet
• solvent in beaker below sample spots
• cover beaker with lid
• leave until solvent front nears top of plate
• locate spots using iodine/UV radiation (or ninhydrin for amino acids)

Question 6

how to make esters

Answer 6

esterification

using concentrated sulfuric acid

Question 7

how to hydrolyse esters in acidic conditions

Answer 7

use dilute sulfuric acid

Question 8

how to hydrolyse esters in alkaline conditions

Answer 8

use dilute sodium hydroxide (forms a carboxylate ion)

Question 9

describe how to test for primary and secondary alcohols

Answer 9

• add acidified potassium dichromate
• primary and secondary react causing a colour change from orange to green
• tertiary doesnt react

Question 10

what does oxidation of primary alcohols produce

Answer 10

aldehyde but if not distilled off it will further oxidise to a carboxylic acid

Question 11

what does oxidation of secondary alcohols produce

Answer 11

ketone

Question 12

describe how to test for phenols

Answer 12

• add neutral iron (iii) chloride to a sample

- colour change of orange to purple

Question 13

describe elimination reactions of alcohols

Answer 13

• passing over heated aluminium oxide catalyst at 300 degrees
• or refluxing with concentrated sulfuric acid
• both produce an alkene and a molecule of water

Question 14

how does infrared spectroscopy work

Answer 14

• infrared radiation is absorbed by covalent bonds
• causes an increase in vibrational energy of the bond
• different bonds absorb different wavelengths
• chemists identify bond from the wavelength absorbed