3.7 Optical Isomerism & 3.8 Aldehydes And Ketones Flashcards
Name Compound CH3C(OH)(CN)CH2CH2CH3
2-hydroxy-2-methylpentanenitrile
How to distinguish between enantiomers
- Use of plane polarised light
- light rotated in oppose directions equally
What type of product is formed when an aldehyde is reduced?
primary alcohol
What is the definition of stereoisomerism?
molecules with the same structural formula but different arrangement of atoms in space
What are optical isomers?
non-superimposable mirror images
What do chiral molecules do to plane-polarised light?
rotate it
What forms when an unsymmetrical ketone reacts with KCN?
A mixture of enantiomers
Why are racemic mixtures optically inactive?
They contain equal amounts of enantiomers which cancel out the optical activity
What is the definition of structural isomerism?
molecules with the same molecular formula but different structural formulae
What forms when a ketone reacts with HCN?
Hydroxynitrile
What is another name of a chiral centre
sterogenic centre
What is a chiral carbon
carbon atom bonded to 4 different groups
Name product formed when pentanal is reduced with NaBH4
pentan-1-ol
What is meant by a sample which is enantiomerically pure
sample which only contains one optical isomer
What is the nucleophile in the reaction of aldehydes with NaBH4
H^-
Why are racemic mixtures optically inactive
They contain equal amounts of enantiomers which cancel out the optical activity
What is the effect of enantiomers on plane polarised light
They rotate the plane of polarised light
Name product formed when butanal is reacted with KCN
2-hydroxypentanenitrile
What is observed when Fehlings reagent is mixed with an aldehyde
brick-red precipitate forms
What is another name for a racemix mixture
Racemate
Name product formed when butanone is reduced with NaBH4
butan-2-ol
Condition needed in reduction of an aldehyde or ketone
acidic solvent
What are enantiomers
Non-superimposable mirror images
What is a racemic mixture
a mixture which contains equal amount of enantiomers
What is the hazard of using KCN
it is highly toxic
State the relationship between two chiral molecules with the same structural formula.
non-superimposable mirror images
Which compound does not show stereoisomerism?
a.
1,2-dichloropropane
b.
1,3-dichloropropene
c.
1,2-dichloropropene
d.
1,3-dichloropropane
d
Give the chemical formula of the reagent used to test for Ba^2+ and the observation made.
reagent : H2SO4
observation : white precipitate formed
Give the chemical formula of the reagent used to test for the SO4^2- and the observation made.
reagent : BaCl2
Observation : white precipitate
Which one of the following statements about but-2-enal, CH3CH=CHCHO, is not true?
A It has stereoisomers.
B It shows a strong absorption in the infra-red at about 1700 cm−1.
C It will turn an acidified solution of potassium dichromate(VI) green.
D It can be dehydrated by concentrated sulphuric acid.
D
Which one of the following reactions will produce an organic compound that has optical isomers?
A dehydration of butan-2-ol by heating with concentrated sulphuric acid
B reduction of pentan-3-one by warming with NaBH4
C addition of Br2 to 3-bromopropene
D reduction of 2,3-dimethylpent-2-ene with H2 in the presence of a nickel catalyst
D
In which one of the following mixtures does a redox reaction occur?
A ethanal and Tollens’ reagent
B ethanoyl chloride and ethanol
C ethanal and hydrogen cyanide
D ethanoic acid and sodium hydroxide
A
because in silver mirror there is an Ag^+ ion (fehlings has Cu^2+ ion) As Ag+ goes to Ag
ethanal therefore gets oxidised as Ag gets reduced
What reagent is used to reduce an aldehyde or a ketone
NaBH4
- leave blank as you need to do the solution again
Only name and complete mechanism
Elimination
CH32COCH2CHO + 4[H] -> CH3CH(OH)CH2CH2OH
Name product of reaction between pentan-3-one and KCN
2-ethyl-2-hydroxybutanenitrile
