chap 5- whats in a medicine

Question 1

what is a primary alcohol

Answer 1

an alcohol where the -OH is bonded to a carbon that is bonded to one other carbon atom

Question 2

what is a secondary alcohol

Answer 2

an alcohol where the -OH group is bonded to a carbon that is bonded to 2 other carbon atoms

Question 3

what is a tertiary alcohol

Answer 3

an alcohol where the -OH group is bonded to a carbon that is bonded to 3 other carbon atoms

Question 4

how are alcohol and water molecules similar

Answer 4

both are polar due to the polarised O-H bond. which causes a strong attractive force between molecules

Question 5

what do the different alcohols produce when oxidised by acidified potassium dichromate

Answer 5

primary- aldehydes and then carboxylic acid
secondary- ketones only
tertiary- aren’t oxidised

Question 6

how do secondary alcohols oxidise to ketones

Answer 6

reflux a secondary alcohol with acidified dichromate (VI) to produce a ketone. Ketones can’t be oxidised easily so even prolonged refluxing wont produce anything more

Question 7

how do you make an alkene from an alcohol

Answer 7

eliminate water from the alcohol in a dehydration reaction

Question 8

what are the 2 methods of dehydrating an alcohol to obtain an alkene

Answer 8

1) pass ethanol vapour over a hot catalyst of pumice stone or Al2O3 (catalyst provides large SA)
2) reflux the ethanol with excess conc sulfuric acid at 170c. then collect the ethene produced over water

Question 9

how can you produce an ester from an alcohol

Answer 9

react the alcohol with carboxylic acid or acid anhydrides

Question 10

alcohol + carboxylic acid=?

Answer 10

ester (in the presence of an acid catalyst) usually conc sulfuric or hcl

Question 11

how can an alcohol be transformed into a haloalkane

Answer 11

alcohols react with compounds containing halide ions in a substitution reaction. The -OH is replaced by the halide

Question 12

what is the formula of phenol

Answer 12

C6H5OH

Question 13

describe the test for phenols

Answer 13

add phenol to neutral iron (III) chloride solution and shake, will turn purple

Question 14

why are phenols described as weak acids

Answer 14

they dissolve a little bit in water to form a phenoxide ion and a H+ ion- weakly acidic

Question 15

what is produced when a phenol reacts with an alkali

Answer 15

salt and water

Question 16

why do phenols not react with carbonate solutions

Answer 16

not a strong enough base to remove the hydrogen ion form phenol

Question 17

how can you tell phenols apart from carboxylic acids

Answer 17

carboxylic acids react with alkalis and carbonates and give off CO2 gas.
phenols don’t react with carbonates and react with strong alkalis

Question 18

how can you test whether something is a phenol or a different alcohol

Answer 18

alcohols and phenols react with acid anhydrides to form an ester and a carboxylic acid.
but phenols will not react with carboxylic acids to form an ester

Question 19

what problem does refluxing avoid

Answer 19

organic reactions are slow and substances are flammable and volatile (low bp) so in a beaker they would evaporate or catch fire before they have time to react

Question 20

how do you carry out reflux

Answer 20

heat the solution in a flask fitted with a vertical liebig condenser- causes the solution to continuously boil/ evaporate and then condense back into the flask giving it time to react.

Question 21

why should reflux be heated electronically

Answer 21

avoids naked flames that could ignite the compoundsq

Question 22

outline the process of distillation

Answer 22

heat a mixture in distillation apparatus, substances will evaporate in order of increasing boiling points, evaporated substance enters condenser cools and condenses back into liquid
it can then be collected, themometer shows bp of substance evaporating at any given time