Chemistry Flashcards
(22 cards)
Butan-1-ol can be oxidised to form butanal.
(i) State a suitable oxidising mixture for this reaction.
H+
Cr2O7^ 2-
Butan-1-ol can be oxidised to form butanal.
State the colour change you would see during this oxidation.
from …………………………………………. to …………………………………………..
(ii) Orange to green/black/blue 1
The reaction in (a) was carried out using distillation and not reflux. Explain why.
distillation (no mark) because distillation allows loss of volatile 1 components /removes butanal from oxidising mixture
prevents formation of RCOOH/ partial oxidation would be achieved 1 or reverse argument for reflux not being used
in that reflux prevents loss of volatile components
hence complete oxidation would be achieved/RCOOH would be formed
Compound E can be oxidised to form a carboxylic acid.
(i) State a suitable oxidising mixture for this reaction.
H+
Cr2O7^2-
Reaction of a sample of citronellol, C10H20O, with hydrogen in the presence of a catalyst results in the formation of a saturated compound C.
(i) Suggest a catalyst for this reaction.
Ni/Pt/Rh/Pd
(ii) Why does lavandulol not have cis-trans isomerism?
(ii) One of the C in both C=C is joined to two atoms or groups that are the same
State a reagent and a catalyst that could be used to form ester X from lavandulol.
CH3COOH 1
H2SO4/H+/HCl (aq) or dilute loses the mark 1
Would you expect the conversion of compound D to compound E to be a first or second
order reaction? Justify your answer.
(e) Primary halogenoalkanes are second order
R burnt with a very sooty flame.
arene/benzene ring
OR high carbon to hydrogen ratio/low hydrogen to carbon ratio aryl. 1 ALLOW “arene or alkene”
R reacted with sodium to give off hydrogen gas.
(ii) contains an OH group/“acid or alcohol” 1
R produced a slightly acidic solution in water, but did not react with sodium carbonate solution.
(iii) phenol/”not a carboxylic acid” 1
(iv) R gave an orange precipitate with Brady’s reagent (2,4-dinitrophenylhydrazine).
(iv) contains a C=O group/carbonyl/”aldehyde or ketone” 1
(v) R did not react when warmed with Benedict’s solution.
(v) a ketone/ “not an aldehyde” 1
(vi) A solution of R rotated the plane of plane-polarised light.
contains a carbon atom with four different groups around it/chiral compound/optical isomers
(vii) The infra-red spectrum of R had an absorption at 830 cm–1.
an arene (1) with two adjacent hydrogen atoms (1)
How do both types of spectra allow the carboxylic acids to be identified and distinguished?
infrared – 1 mark only –1 shows (very broad) peak between 2500–3300 (cm )
(due to O–H bond)
ALLOW (very broad) peak around 3000 (cm–1) OR any stated
value between 2500 and 3300 (cm–1) for O–H
DO NOT ALLOW peak in range 3200–3550 (cm–1)
IGNORE any reference to C=O or C–O as both are also present in an ester OR to fingerprint region
13C NMR – 2 marks
(CH3)2CHCH2COOH has 4 peaks (due to 4 different C environments) (CH3)3CCOOH has 3 peaks (due to 3 different C environments)
ALLOW ‘13C NMR detects the number of/different C environments’ for 1 , suitable example for the 2nd mark 3
(i) State the general formula of an α-amino acid.
H2NCHRCOOH
The mixture of tripeptides can be analysed by using gas chromatography, coupled with mass spectrometry.
Summarise how each method contributes to the analysis.
gas/liquid chromatograph separates the tripeptides (1)
mass spectrometer produces a distinctive fragmentation pattern (1) identification by computer using a spectral database (1)
(i) State what is meant by the term zwitterion.
(b) (i) molecule/ion/’it’ has both + and – charges
State suitable reagents and conditions to break down a protein into amino acids.
heat/warm/reflux (1)
named strong acid/base
an enzyme (which need not be named) (1)
NOT conc HNO3 or conc H2SO4
- (a) Define the term oxidising agent in terms of electrons.
gains electrons (1)
Why is methyl orange not suitable as an indicator for the titration of HX with sodium hydroxide?
Weak acid/strong base ∴pH at equivalence > 7 (1)
methyl orange has colour change at pH < 7 (1)
