alcohols Flashcards
(26 cards)
description of an aldehyde
functional group CHO
carbonyl bonded to at least one H atom
name ends in …al
description of a ketone
functional group is CO
carbonyl bonded to two C atoms
name ends in ….one
description of a carboxylic acid
functional group is COOH
carbonyl bonded to an OH group
name ends in …oic acid
alcohol classification
primary alcohol- C bonded to OH is bonded to one other C
secondary alcohol - C bonded to OH is bonded to two other C
tertiary alcohol - C bonded to OH is bonded to three other C
observation for alcohol oxidation
orange to green
acidified K2Cr2O7 is used as an oxidising agent
primary alcohol to aldehyde
reagent - acidified K2Cr2O7
conditions - heat under distillation
CH3CH2OH + [O] -> CH3CHO + H2O
aldehyde to carboxylic acid
reagent - acidified K2Cr2O7
conditions - heat under reflux
CH3CHO + [O] -> CH3COOH
primary alcohol to carboxylic acid
reagent - acidified K2Cr2O7
conditions - heat under reflux, excess oxidising agent
CH3CH2OH + 2[O] -> CH3COOH + H2O
oxidation of secondary alcohols
reagent - acidified K2Cr2O7
conditions - heat under reflux/distillation
CH3CH(OH)CH3 + [O]-> CH3COCH3 + H2O
features of a condenser
open at both ends
cold water flows around outside
purpose of a condenser
cools hot vapour and condenses to liquid
purpose of anti bumping granules
prevent the formation of large bubbles
why is reflux used to oxidise a primary alcohol to a carboxylic acid
reflux doesnt allow any reactant vapour to escape
model answer
describe when a reaction mixture is refluxed
-ethanol and acidified potassium dichromate (vI) are heated to boiling point for a prolonged time
-ethanal vapour is formed which escapes from the liquid mixture and is then condensed back into liquid and returned to the reaction mixture
-any ethanol and ethanal that initially evaporates can then be oxidised
what happens to an aldehyde as it is produced during distillation
the aldehyde forms as a vapour and escapes from the reaction mixture into the condenser
tollens reagent - [Ag(NH3)2]+
used to test aldehydes
silver mirror forms
when no aldehyde no visible change
fehlings solution - Contains Cu2+
used to test for aldehydes
forms brick-red precipitate
test for carboxylic acids -
Na2CO3 forms effervescence
Producing ethanol from crude oil
Hydration
Hydration
Ch2=ch2 + h2o -> ch3ch2oh
Conditions - conc h3po4 catalyst, steam , 450c temp, 50-100atm pressure
Producing ethanol from fermentation
C6h12o6 -> 2ch3ch2oh + 2co2
Conditions - yeast enzymes (zymase) , 35c temp , no oxygen
Advantages of hydration of ethene
Large scale production method
High purity product made
High rate of reaction
Continuous production method
Disadvantages of hydration of ethene
High temp and pressure which increases cost
Expensive and high tech equipment needed
Fermentation advantages
Uses renewable resources
Low tech suitable for developing countries and little expensive equipment needed
Fermentation disadvantages
Slower rate of reaction
Impure product made that still needs distilling
