ANSWERS TO EXERCISES AND REVISION QUESTIONS(iii) CH 3 —CN—NH 2 (iv) CH 3 CH 2 COOH
|
H
18I
(i)butanoic acid (ii)heptanoic acid
(iii)butane-1,4-dioic acid.
18J
(i)CH 3 COOH, CH 2 BrCOOH, CH 2 ClCOOH, CHCl 2 COOH,
CCl 3 COOH, CF 3 COOH
(chlorine is more electronegative than bromine).
18K
(i)(a) methyl ethanoate CH 3 COOCH 3
(b) ethyl octanoate C 7 H 15 COOCH 2 CH 3
(c) methyl methanoate HCOOCH 3
(d) diethyl oxalate ( diethyl ethanedioate) (COOCH 2 CH 3 ) 2.
(ii)(a) propanoic acid, methanol
(b) methanoic acid, ethanol
(c) ethanoic acid, propan-1-ol
(d) chloroethanoic acid, methanol.
18L
NH 3 , CH 3 NH 2 , CH 3 NHCH 3.
18M
(i)Middle C has an asterisk.
(ii)2 methylbutan-1-ol, 2-bromo-1-chlorobutane.
18N
(i)(ii) CH 3 CHCOO–
|
NH 3 +18O
(i)
O
||
H 2 NCH 2 C—NHCHCOOH
|
CH 3
(ii)Gly-Ala-Cys, Gly-Cys-Ala, Cys-Gly-Ala, Cys-Ala-Gly,
Ala-Cys-Gly, Ala-Gly-Cys (six in all)
Revision questions
18.1 (i) CH 3 CH 2 CH 2 CH 2 CHOHCH 3
(ii) CH 3 COHCH 3
|
CH 3
(iii) CH 2 OHCH 2 CHOHCH 3
(iv)18.2ethanol, water, phenol, ethanoic acid.
18.3
(i) CH 3 CH 2 CH 2 CHCH 2 CHO
|
CH 3
Notice the aldehyde group contains the carbon atom
numbered 1.
(ii) CH 3 COCH 2 COCH 3 (iii)(iv) CH 3 CHCOOH (v) COOH
||
CH 3 CH 2
|
CH 2
|
COOH
18.4oxalic acid
18.5 (i)CH 3 CH 2 COOCH 2 CH 3 (ii)CH 3 CH 2 CH 2 OH
(iii)CH 3 (CH 2 ) 3 COOH (iv)CH 3 COOH18.6 (i)HCOOCH 2 CH 2 CH 3 (ii)HCONH 2
(iii)HCOCl.
18.7 *
(i) CH 2 OHCHCOOH
|
NH 2
(ii)Yes, it has a carbon atom attached to four different
groups, marked ‘*’.
(iii) HO 2 CCHCOOH
|
NH 2
O
||
(iv) CH 2 OHCHC—NHCHCOOH
||
NH 2 CH 2 OH
18.818.918.10 (i)ester (ii)amino group
(iii)ester and carboxylic acid (iv)amide
(v)phenol, alcohol, amino (vi)halogen.
18.11 (i)X would form an orange precipitate with 2,4-
dinitrophenylhydrazine.
(ii)X would reduce Tollens’ reagent or Fehling’s solution.
(iii)CH 3 CH 2 CHO; to confirm this, check the melting point
of the DNP derivative against that in a data book.Unit 19
Exercises
19A
Heat the sample of sea water to dryness, so that all the
water is evaporated off. The solid left would not be pure
sodium chloride, because sea water contains other
dissolved salts such as magnesium chloride and
potassium chloride.
19B
(i)A separating funnel.
(ii)Add mixture to water and stir separate sand off by
gravity filtration wash sand well and dry in an oven
filtrate contains dissolved sugar evaporate water from
filtrate to obtain concentrated solution (solid sugar
decomposes when heated, so this is ‘safer’ than
evaporating solution to dryness) allow concentrated
solution to cool and sugar crystals should separate out
filter solution to remove sugar crystals.
(iii)Dissolve the mixture in water at a temperature just
less than 100 °C cool solution to 20 °C crystalline
potassium chlorate separates out, which can be removed
by filtering (potassium chloride remains in solution).
(iv)Fractional distillation will result in a mixture much
more rich in the volatile component (the one that boils at
60 °C) collecting in the receiving container.
(v)Simple distillation.
19C
(i)Let the amount of X in the organic layer bexg, then
K x/200
d^7 (1 x)/100
orx0.93 g.
(ii)First extraction: let the amount of X in the organic
layer be zg, then
K z/100
d^7 (1 z)/100Thereforez0.875 g, i.e. 0.125 g left in the aqueous
layer.
Second extraction: let amount of X in organic layer be yg,
then
K y/100
d^7 (0.125 y)/100
Therefore,y0.109 g and the total amount extracted is
0.8750.1090.98 g
that is, 0.05 g more than for one extraction.
19D
(i)
R yz
ffor A xyz(ii)
R z
ffor B xyzRevision questions
19.1 (i)evaporation
(ii)simple distillation
(iii)fractional distillation
(iv)fractional distillation
(v)column chromatography
(vi)separation using a separating funnel
(vii)stir mixture in water filter to remove chalk
evaporate off water from filtrate to give salt.
19.2Paper chromatography using propanone as solvent.
If substances are not all coloured, use a suitable method
to develop the spots.
19.3Sublimation – ammonium chloride ‘sublimes’,
potassium chloride does not.
19.4 (i)paper chromatography (or TLC)
(ii)column chromatography. Ethanol can be used as
solvent in both techniques.
19.5Paper chromatography spot urine and spots of
amino acids it is thought to contain on the paper run
chromatogram using a suitable solvent (water)
develop colourless spots by spraying with ninhydrin.
19.6Gas chromatography compare retention times of
components of mixture with the retention times of known
alcohols (or use GC–MS!).
19.7Paper chromatography compare pattern of spots
of suspect ink with a sample of ink obtained from the
forged cheque.
19.8Let mass extracted be xg, then3.5 x/50
(0.5 x)/150
i.e.x0.27 g.
19.9
(i)Area ABC 1/2 16 40 320 mm^2
Area PQR 1/2 20 32 320 mm^2
(ii)The same area under each of the peaks suggests there
are equal amounts of each constituent in the mixture.
(iii)You could cut out each peak from the chart and
weigh them, then compare masses.
19.10Dissolve ‘dyes’ from smarties by stirring them in a
littlewater. Use paper chromatography to see if more
than one spot occurs.Unit 20
Exercises20A
Rearranging, c gives c 98 MHz 98 000 000 Hz, therefore
3.00^108
9.8 107 3.1 m4490230_000118_2 9 _Ans.qxd 3/2/06 2:22 pm Page 449