Module 6 - Organic Chemistry & Analysis - Exam Questions Flashcards
What does the symbol [H] represent? (1)
Reducing agent
Suggest a reagent that would convert the -OH group in phenol to an -O(-) group (1)
NaOH
Explain what is meant by the term 1,4-diamino (2)
Diamino: two amine groups
1,4: Their position on the ring
1,4-dinitrobenzene is converted to 1,4-diaminobenzene, what type of reaction is this? (1)
Reduction
State reagents and conditions required to convert 1,4-dinitrobenzene to 1,4-diaminobenzene (2)
Tin and HCl
Conc acid under reflux
Explain how the amino groups in a primary amine allow the molecule to act as a base (2)
Accepts H+ using the lone pair on N
Which forms a dative covalent bond
State whether you would expect hexane-1,6-diamine to be a stronger or weaker base than 1,4-diaminobenzene. Explain your reasoning (3)
Hexane-1,6-diamine is a stronger base because:
Electrons move towards the N in hexane-1,6-diamine
Lone pair from N is partially delocalised around the ring in diaminobenzene
So electron pair is more easily donated
Suggest possible problems of making a chiral drug such as salbutamol and describe two
ways that the pharmaceutical industry might overcome these problems (4)
Production of a single isomer is more expensive One of the isomers is more active Overcome by using: Enzyme catalyst Chiral catalyst
Explain what is meant by an α-amino acid (1)
Both NH2 and COOH are joined to the same C
Explain the evidence that led scientists to doubt the model proposed by Kekulé (3)
Bond length intermediate between/different from (short) C=C and (long) C–C
ΔH hydrogenation less exothermic than expected
Only reacts with Br2 at high temp or in presence of a halogen carrier
The chemist observed that bromine decolourises when it reacts with phenol
What other observation would she have made? (1)
White precipitate
Cyclohexene also decolourises bromine
Name the organic product formed (1)
1,2-Dibromocyclohexane
Explain the relative resistance to bromination of benzene compared to phenol and compared to cyclohexene (5)
Benzene - π bonds are delocalised Phenol - a lone pair of electrons on the OH is partially delocalised into the ring Cyclohexene - electrons are localised Benzene has a lower electron density Benzene cannot induce a dipole in Br2
State the general formula of an α-amino acid (1)
C bonded to NH2, COOH, H and R
The mixture of tripeptides can be analysed by using gas chromatography, coupled with mass spectrometry. Summarise how each method contributes to the analysis (3)
Gas chromatograph separates the tripeptides
Mass spectrometer produces a distinctive fragmentation pattern
Identification by computer using a spectral database
State what is meant by the term zwitterion (1)
Ion has both + and - charges
What is meant by the term stereoisomer? (1)
Molecules with the same structure but different arrangements in space
How does cis-trans isomerism arise in organic molecules? (1)
Double bond does not rotate
State a use for Kevlar (1)
Bullet proof clothing
Kevlar is formed from a diamine and a dioic acid, what kind of polymerisation is this reaction? (1)
Condensation`
Chlorobenzene can be nitrated to form a mixture of products. Suggest why the reaction forms a mixture of products (1)
Nitration at different positions on the ring
State what the biochemist would see when hydroxyethanal reacts with
Tollens’ reagent (1)
Silver mirror
The biochemist also reacted hydroxyethanal with acidified dichromate by heating
under reflux. Write an equation for this oxidation. [O] is oxidising agent (2)
HOCH2CHO + 3[O] -> HOOCCOOH + H2O
The biochemist then reduced hydroxyethanal using aqueous NaBH4.
Write the structural formula of the organic product (1)
HOCH2CH2OH
