Download 1 Pioneer Junior College 9647/9746 H2 Chemistry Banding Lecture

Pioneer Junior College
9647/9746 H2 Chemistry Banding Lecture (Band 2)
Organic Chemistry
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Isobutylene, also known as 2-methylpropene, has significant industrial importance. It is
the starting material for Methacrolein, which is a chemical used in the production of
polymers.
(a) State the type of reaction and show the mechanism for its reaction with hydrogen
bromide.
(b) Give the structural formulae of the two possible products formed in (a).
(c) Draw the two possible carbocations formed in the reaction and explain why one
is formed in greater proportion over the other.
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(a)
Nitrobenzene is prepared by reacting benzene with a nitrating mixture
(i)
Describe the mechanism for the formation of nitrobenzene from benzene.
(ii) During the nitration reaction, a di-substituted product is also formed. Draw
the likely structure of this product.
(b)
Iodine monochloride, ICl, can be prepared by passing chlorine gas over iodine
crystals and it is collected as a dark brown liquid.
Draw the structure of the likely organic product for the reaction of methylbenzene
and ICl in the box below.
(a)
Give the structural formula of the organic products formed when Compound X is
reacted with the following reagents.
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(i)
(ii)
(iii)
Br2 (aq)
NaOH (aq), heat
Cl2 (aq)
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(b)
Give the structural formula of the organic products formed when Compound Y is
reacted with the following reagents.
CH3
CH3
Compound Y
(i)
(ii)
Br2 (aq)
Cold alkaline KMnO4 (aq)
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Potassium bromide in concentrated sulfuric acid is used as a reagent in the following
reaction scheme. It is found that organic compound Q produces white fumes when
subjected to PCl5, and has no reaction with alkaline aqueous iodine. Deduce with
reasons, the structure for compounds P to T.
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(a)
Describe the following conversions, stating the intermediates and the reagents
and conditions required for each of the conversions.
(i)
CH3CH2CH2NH2 from CH3CH2OH
(ii) CH3COCH2OH from CH3CH=CH2
(b)
A
(i)
(ii)
B
C
Arrange the compounds in order of increasing pKa. Explain your reasoning
Explain why compound C is insoluble in water but soluble in aqueous
sodium hydroxide
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Compound Y is generally known as Menthol. It can be found naturally in peppermint oil
Compound Y
(a)
(b)
(c)
(d)
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Identify S, T, U and V
State the type of reaction that occurs when Y is transformed into T
T can also be prepared from S. Suggest the reagents and conditions for this
conversion.
Suggest simple chemical tests to identify the functional group present in U.
The following method was proposed by a student
Identify and explain 3 errors present in his choice of reagents.
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(a)
(i)
(ii)
Draw the structures of compound B, D and E in the boxes provided.
Suggest reagents and conditions required in steps I and II.
(b)
Suggest a simple chemical test that can be used between adrenalin and the
following compound.
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The folowing reaction scheme shows the reactions of benzaldyde.
benzaldehyde
(a)
(b)
(c)
Write the formula of compounds Q to T.
Suggest reagents and conditions for Step 1 and 2.
Name and describe the mechanism of Step 1.
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(a)
(b)
(c)
(d)
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State the reagents and conditions of steps II to IV.
Draw the displayed formula of organic compound R.
Name the type of reaction in step II and briefly describe why this is not a good
method to obtain compound Q.
Describe a simple chemical test to distinguish between compound P and
compound Q.
Pyruvic acid can be synthesized from ethanoic acid via the following reaction scheme
(a)
(b)
(c)
(d)
Give the reagents and conditions for steps I and II.
Draw the structure of compound X.
Describe the mechanism for the reaction of CH3COBr with KCN to form X.
Pyruvic acid can be reduced to lactic acid, CH3CH(OH)CO2H.
Give the reagents and conditions for this reaction.
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Complete the following reaction scheme, giving the structures of intermediate A and B
and the reagents and conditions for step I, II and III.
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Describe a chemical test that would distinguish the following compounds
(a)
(b)
(c)
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14
The structural formula of a compound Z is shown below
Draw the stuructural formula of the organic products when Z undergoes reaction with
the following.
(a)
(b)
(c)
(d)
(e)
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Alkaline I2
H2SO4 (aq), heat
2,4-DNPH
Ethanoyl chloride
Phosphorus pentachloride
The scheme below shows the final stages in the synthesis of compound M
(a)
(b)
(c)
Draw the structural formulae of compounds L and K.
Give the synthetic route, involving not more than 3 steps, from J to K.
Give the products when compound M reacts with
(i)
Sodium metal
(ii) Bromine water
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Compound P has the molecular formula C5H12O. When P is heated with acidified
potassium dichromate (VI), the solution remains orange, when P is reacted with
excess concentrated sulfuric acid at 180oC, a mixture of two isomers, Q and R, is
produced. When reacted with hot concentrated potassium managanate (VII), Q
produces effervescence, while R gives no effervescence. When either Q or R is
reacted with dry hydrogen chloride gas at room temperature, compound S is produces
as the major product.
Deduce, with reasons, the structures of all compounds P to S, writing balanced
equations where appropriate.
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Optimum amino acid balance is important to maximize growth and efficiency in pigs.
Information of the 3 amino acids in the pigs fed is listed below
(a)
(b)
(c)
(d)
(e)
Draw the structural formula of the dipeptide, Lys-Trp.
Draw the structure of threonine at pH 5.60.
Electrophoresis was run to separate a solution containing the 3 amino acids at
pH 7.00 and the relative positions of the amino acids are obtained in the following
diagram
Draw the structure of the amino acids at A, B and C.
Predict the relative basicity of Tryptophan and Lysine.
Draw the structural formula of the organic product when:
PCl5 is added to threonine.
(i)
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(ii)
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Ethylamine can be synthesised by reacting ammonia with chloroethane.
(a) State the reagents and conditions for the reaction.
(b) Chloroethane may be converted to dipropylamine by the following route
(i)
(ii)
(iii)
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propanoyl chloride is added to tryptophan.
(a)
Suggest reagents and conditions for stages I and II.
Draw the structural formulae of E and F.
Describe the mechanism in stage I.
Draw the structural formula of the organic products formed in the spaces
provided.
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(b)
3 amino acids with their R groups and isoelectric points are given in the table
below.
(i)
(ii)
(iii)
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Draw the structural formula of a tripeptide with the sequence histidineglycine-glutamic acid showing the form in which it would exist at pH 2.
By means of balanced equations, show how glycine can act as a buffer.
Suggest with reasons a suitable pH which can be used to separate a
mixture of histidine, glutamic acid and glycine using electrophoresis.
Enzyme A digests proteins at the carboxylic acid end of the amino acid valine, val. The
following peptides were identified after digestion of a polypeptide with enzyme A.
Asp-Ser-Gly-Val
Ser-Phe-Cys
Phe-Val
Another enzyme B digests at the carboxylic acid end of serine, ser. The following
peptides were identifies after digestion of the same polypeptide.
Gly-Val-Ser
Phe-Cys
Phe-Val-Asp-Ser
Use the information to determine the primary structure of the polypeptide.
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A polypeptide chain was digested with an enzyme (digesting at the carboxyl end of
leucine). A particular section of this polypeptide was found to yield the following:
Glu-Ala
Val-Leu
Glu-Asp-Thr-Leu
Ala-Glu-Leu
Another enzyme digests glutamic acid at the carboxyl end and the following peptides
were obtained.
Ala
Val-Leu-Glu
Asp-Thr-Leu-Ala-Glu
Leu-Glu
Deduce the sequence of the polypeptide chain.
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