Organic Chemistry H2 Questions MCQ

Organic Chemistry MCQ (12)1, 19 Covalent bonds are formed by orbital overlap. The shape of unsaturated hydrocarbon molecules can be explained in terms of hybridisation of orbitals. Which bond is not present in HC≡CCH2CH=CH2? A. B. C. D.

A π bond formed by 2p-2p overlap A σ bond formed by 1s-2sp overlap A σ bond formed by 2sp-2sp2 overlap A σ bond formed by 2sp2-2sp3 overlap

(12)1, 20 When heated with chlorine, the hydrocarbon 2,2-dimethylbutane undergoes free radical substitution. In a propagation step, the free radical X· is formed by the loss of one hydrogen atom.

H3C H3CH 2C

+

CH3

Cl

X

+

HCl

CH3 How many different forms of X· are theoretically possible? A. B. C. D.

1 2 3 4

(12)1, 21 PGE2 and PGF2α are two prostaglandins, both with pharmacological activity. HO

O

CO 2H

CO 2H

CH3

CH3 HO

HO

HO

PGE2 A. B. C. D.

H2/Ni H2/Pt H2O/H+ NaBH4

HO

PGF2α

(12)1, 22 The diagram shows the structure of the naturally-occurring molecule cholesterol. H3C CH3 CH3

H CH3

H

H

H3C H

HO

Cholesterol reacts with cold, dilute acidified KMnO4. Four students made claims about this reaction. W

The cyclohexene ring becomes saturated.

X

The cyclohexene ring is broken open.

Y

The number of chiral centres increases by 1.

Z

The number of chiral centres increases by 2.

Which students’ claims are correct? A. B. C. D.

W and Y W and Z X and Y X and Z

(12)1, 23 The diagram represents the transition state of an SN2 reaction in which N is an anionic nucleophile and L the leaving group, but without any indication of the location of positive or negative charges. CH3

H3C N

C CH3

Which is a possible combination of charges? A B C D

Charge on N δδδ+ δ+

Charge on L δ+ δδ+ δ-

L

(12)1, 24 Chlorofluorocarbons (CFCs) have been widely used in aerosol sprays, refrigerators and in making foamed plastics, but are now known to destroy ozone in the upper atmosphere. What will not destroy ozone, and therefore can be used as a replacement for CFCs? A. B. C. D.

CHBr3 CCl3CBr3 CHClFCClF2 CH3CH2CH2CH3

(12)1, 25 Rosmarinic acid occurs in culinary herbs such as rosemary, sage and thyme. OH O

OH

OH

O O HO OH

How many moles of NaOH(aq) will react with one mole of rosmarinic acid when the acid is heated under reflux with an excess of NaOH(aq)? A. B. C. D.

4 5 6 7

(12)1, 26 Cattle suffering from stress produce 6-methylhept-5-en-2-one, which repels mosquitos. (CH3)2C=CHCH2CH2COCH3 Which property will 6-methylhept-5-en-2-one possess? A. B. C. D.

Addition of Br2(aq) produces a chiral compound. Prolonged heating with acidified concentrated KMnO4 produces HO2CCH2CO2H. Reduction by a methanolic solution of NaBH4 produces a compound C8H18O. Warming with alkaline aqueous I2 produces CH3CO2H.

(12)1, 27 What stabilises the α-helix of proteins? A. B. C. D.

Disulfide bridges and hydrogen bonding Disulfide bridges only Hydrogen bonding only Van der Waals’ forces only

(12)1, 28 After the reduction of nitrobenzene to phenylamine using tin and concentrated hydrochloric acid, an excess of sodium hydroxide is added. What is the purpose of the sodium hydroxide? A. B. C. D.

To dry the product To liberate the phenylamine To lower the boiling point for subsequent distillation To precipitate tin(II) hydroxide

(12)1, 29 Why are amides, RCONH2, less basic than amines, RNH2? A. Amides form zwitterion in which the nitrogen atom carries a positive charge. B. Amides have a resonance structure involving the movement of a pair of electrons from nitrogen atom to the oxygen atom. C. Electrons on the nitrogen atom move on to the C-N bond giving it some double character so that it is more difficult to break. D. The amide carbonyl group withdraws electrons from the NH2 group to make the hydrogen atoms acidic.

(12)1, 30 When 2-methylphenylamine reacts with an excess of Br2(aq), one of the intermediates is cation Z. NH2

NH2

CH3

Br

CH3

+

H

Br

What is the final product of this reaction? A

B

C

D

NH2

NH2

NH2

NHBr

CH3

Br

Br

CH3

Br

Br

Br

Br

CH3

Br

Br

(12)1, 37 During the preparation of many organic compounds by-products are formed. This usually occurs because the reagents can react in more than one way depending on the conditions used or because the products formed may react with the reactants. Propan-1-ol is produced by the reaction between 1-bromopropane and aqueous sodium hydroxide.

What could be a by-product of this reaction? 1. CH3CH=CH2 2. CH3CH2CH2ONa 3. CH3CH(OH)CH3

(12)1, 38 The mould Phytophthora damages many plants, destroying agricultural crops such as potatoes. A hormone-like compound called alpha1 regulates the reproduction of all species of Phytophthora. The structure of alpha1 is now known, giving scientists a key to the possible future eradication of the mould. O CH3

HO

OH CH3

CH3

OH

CH3

Which will react with alpha1? 1. Cl2(g)/light 2. SOCl2 3. H2/Pt (12)1, 39 Bromoethene, CH2=CHBr, is unreactive to nucleophiles whereas 3-bromopropene, CH2=CHCH2Br, is very reactive by comparison. What could be a reason for the lack of reactivity of CH2=CHBr? 1. The electrons of the bromine atom delocalise into the π bond. 2. The electrons of the π bond repel the attacking nucleophile. 3. The presence of the π bond prevents free rotation of the C-Br bond thus decreasing the reactivity.

(12)1, 40 In an industrial process, heptane vapour is passed over a heated catalyst to make methylbenzene. CH 3CH 2CH 2CH 2CH 2CH 2CH 3

CH3

+

4 H2

Under similar conditions, which of the C8H18 isomers could give 1,4-dimethylbenzene? CH3

H3C H3CH 2C

1

CHCH 2CH 2CH 2CH 3 H3C

H3C

CH3

2 CH3

CH3

H3C CHCH 2CH 2CH 2CH 2CH 3 H3C

3 (11)1, 19

Which statement about the molecule but-2-yn-1-ol is not correct? OH H3C

4

A. B. C. D.

3

2

1

The centre carbon atoms (2 and 3) are sp hybridised. The molecule decolourises warm acidified KMnO4. The terminal carbon atoms (1 and 4) are sp2 hybridised. The terminal carbon atoms (1 and 4) have tetrahedral geometry.

(11)1, 20 The complete combustion of alkanes to produce carbon dioxide and water is an important exothermic reaction. Which line on the graph shows the relationship between the number of carbon atoms in the alkane and the number of moles of oxygen gas needed for complete combustion of the alkanes? A B

Number of moles of oxygen gas

C

D

1

Number of carbon atoms in alkane

(11)1, 21 Chloroethene, CH2=CHCl, is unreactive to nucleophiles whereas 3-chloropropene, CH2=CHCH2Cl, is very reactive by comparison. What explains the lack of reactivity of CH2=CHCl? A. Substituted alkenes undergo only electrophilic addition. B. The C=C double bond and the Cl atom are both electron withdrawing which stabilises CH2=CHCl. C. The electrons on the Cl atom delocalise into the π bond. D. The presence of the π bond prevents free rotation of the C-Cl bond thus decreasing the reactivity.

(11)1, 22 Which species could be an intermediate in an SN1 substitution? OH

A H3C

Cl O

-

+

B

CH2

CN

C

+

H

H3C

D HO

-

CH3 C

Br

-

CH3

(11)1, 23 The diagram shows a reaction.

steam, H+ CH 2CO 2

Z

What could be the final products Z?

A

B

CH 2CO 2H

CH 2CO 2H

+ +

HO

HO

OH

OH

C

CH 2CO 2H

+

HO

D

CH 2OH

+

HO 2C

OH

(11)1, 24 A comparison is made of the rate of hydrolysis of four halogenocompounds by warm NaOH(aq). CH3CH2COCl

C6H5Cl

(CH3)3CBr

(CH3)3Cl

X

Y

Z

W How will these rates compare? Fastest W W X Z

A B C D

Y Z Z Y

Slowest X X W W

Z Y Y X

(11)1, 25 The reaction conditions for four different transformations are given below. Which transformation has a set of conditions that is not correct? UV

A

CH4(g) + Cl2(g)

CH3Cl + HCl

light

conc. H2SO4

B

C6H6(l) + HNO3(conc.)

55 °C

CH3

CH3

(l) + Cl2(aq)

C

C6H5NO2 + H2O

AlCl3(s)

+ HCl

heat Cl

OH

OH NO 2

D (aq) + HNO3(dilute)

+ H2O

(11)1, 26 Compound P, C4H10O2, is an alcohol containing two –OH groups per molecule. It can be oxidised in stages to compound Q, C4H8O2, and then to compound R, C4H6O2, which is a diketone. Which pair of statements about the properties of P, Q and R is correct? Has 2 chiral centres

A B C D

Reacts with alkaline aqueous iodine to give tri-iodomethane P, Q and R Q and R only Q and R only P, Q and R

P only P only P and Q only P, Q and R

(11)1, 27 In the following two-step synthesis, Y a solid which is insoluble in water, is one of the components in the final reaction mixture. CO 2H

NH3

PCl5, warm

Y

X

CO 2H

then heat

What is Y? A

B CO

NH CO

C CONH 2 CH 2OH

D CO 2

-

CH 2NH 3

-

CO 2 NH 4 +

+

CH 2NH 2

(11)1, 28 Compounds X, Y and Z all react with sodium to release hydrogen but only one of them reacts with 2,4-dinitrophenylhydrazine reagent. Which combination could be X, Y and Z?

A B C D

X

Y

Z

CH 2OH

CHO

CO 2 H

CH 2OH CH 2OH

CHO CH 2OH

CO 2 H CHO

CH 2OH

CH 2OH

CHO CH 2OH

CO 2 H CHO

CHO CH 2OH

CO 2H CHO

CO 2 H CO 2 H

CO 2H

CO 2 H

CO 2 H

(11)1, 29 The compounds responsible for the umami flavour of soy sauce are salts of glutamic acid. HO2CCH2CH2CH(NH2)CO2H Glutamic acid has pKa values of 2.1, 4.1 and 9.5. What is the structure of the major species in a solution of glutamic acid at pH 7? A

B +

H2N O 2C

-

H3N CO 2

-

O 2C

C

CO 2

-

D +

+

H3N

H3N HO 2C

-

CO 2

-

HO 2C

CO 2H

(11)1, 30 Oseltamivir is an anti-viral drug. OR CH 3COHN

[-OR is inert] H2N

What is the product when oseltamivir is heated with HCl(aq)? A

B OR

OR +

H3N

CH 3COHN

+

+

H3N

H3N

CO 2CH 2CH 3

C

CO 2H

D OR

OR

+

H3N

CH 3COHN

+

H3N

+

CO 2CH 2CH 3

H3N

CO 2H

(11)1, 33 The three compounds X, Y and Z have the following structures. HO CO 2CH 3

N

N N

N

CH=CH

2

N O

OH

X Which statements about X, Y and Z are correct? 1. X and Z have the same empirical formula. 2. X and Y are isomers. 3. The Mr of Y is exactly twice that of Z.

Y

Z

(11)1, 37 Swine flu has caused great concern internationally. One widely used treatment is the antiviral drug Tamiflu. O

OCH 2CH 3

(H3CH 2C) 2HCO

NH2 NH O CH3

Which statements about the Tamiflu molecule are correct? 1. It contains an amide group. 2. It contains two ester groups. 3. It contains four chiral centres. (11)1, 38 A catalytic converter is part of the exhaust system of many modern cars. Which reactions occur in a catalytic converter? 1. 2. 3. (11)1, 39 Baeyer’s reagent is used to detect carbon-carbon double bonds: a dilute alkaline solution of KMnO4 loses its pink colour in the presence of such a bond. In which tests does a positive result involve a reduction in the oxidation number of the metal present in reagent? 1. Baeyer’s test 2. Fehling’s test 3. Tollens’ test

(11)1, 40 Spider silk is a protein composed mainly of the three amino acids alanine, glycine and serine. NH2CH(CH3)CO2H

NH2CH2CO2H

NH2CH(CH2OH)CO2H

Alanine

glycine

serine

Which type of bonding can occur in the tertiary structure of spider silk? 1. Van der Waals’ forces 2. Hydrogen bonding 3. Ionic bonding