PHARMACEUTICAL ORGANIC CHEMISTRY | PAST PAPER | PST NTA LEVEL 5

PHARMACEUTICAL ORGANIC CHEMISTRY | PAST PAPER | PST NTA LEVEL 5

This section consists of TEN questions with each question carrying one . Read each question and circle only one correct answer. Dirty work will not be ed

1.      p-nitrotoluene(methyl benzene) on reaction with chlorine forms hydrogen chloride and
a) p-Nitrobenzyl chloride
b) o-Nitrobenzyl chloride           
A
c) m-Nitrobenzyl chloride    
d) Nitrobenzyl chloride

2.      On heating aqueous solution of benzene diazonium chloride, which of the following is formed?
a) benzene
b) chlorobenzene
c) phenol                                    
B
d) aniline

3.      Ether is more volatile than an alcohol having the same molecular formula. What is the reason for this difference?
a) dipolar character of ethers

4.      b) alcohols having resonance structures
c) inter-molecular hydrogen bonding in ethers                                
D
d) inter-molecular hydrogen bonding in alcohols

5.      Ethers may be used as solvents because they react only with which of the following reactants?
a) Acids
b) Bases                                
A
c) Oxidising agent
d) Reducing agents

6.      Carboxylic acids are more acidic than phenol and alcohol because of which of the following?
a) Intermolecular hydrogen bonding
b) Formation of dimmers                       
D
c) Highly acidic hydrogen
d) Resonance stabilization of their conjugate base

7.      the above structure represent

a)      Ketone

b)      Aldehyde                  A

c)      Ether

d)      Ester

8.      Dimethyl ketone can be sometimes called

a)      Acetone

b)      Methylketon                     A       

c)      Ethylketone

d)      Acetophenone

9.      Ketones can be prepared in one step from which of the following process?
a)Hydrolysis of esters
b) Oxidation of primary alcohol
c) Oxidation of secondary alcohol               
C
d) Reaction of acid halide with alcohols

10.  Hydrolysis of ester leads to the formation of which of the following products in basic medium?
a) Ether and alcohol
b) Alcohol and sodium carboxylate                
B
c) Aldehyde and alcohol
d) Sodium carboxylate

 

11.  The substituent groups that are commonly associated with benzene ring are
a) Phenyl and benzyl
b) Propyl and phenyl             
A
c) Methyl and benzyl
d) Butyl and phenyl

 

 

 

Section B Multiple true and false 20%

·         Write the word TRUE and NOT letter T for a correct statement and the word FALSE NOT letter F for incorrect statement in the space provided before each option

·         All responses should be in CAPITAL letter

·         one  will be awarded for each correct response

·         Response with letters T and F will not be awarded any

·         There will be a penalty of half of allocated  for responses with small letters

 

1.      Regarding Acyl chlorides

a)      An acyl chloride like ethanoylchloride is colourless fuming liquid..............TRUE

b)      The strong smell of acyl chloride is the smell of ethanoic acid and acrid smell............TRUE

c)      They dissolve in water meaning that they are soluble in water ...................FALSE

d)      Boiling point of acyl chlorides is 51C...............TRUE

e)      They are polar molecules, and so have dipole-dipole attractions between their molecules as well as van der Waals dispersion forces…………...TRUE

2.      Concerning ethers the following are true

a)      Ethers are compounds with general formula R-O-R`.................TRUE

b)      Where R can be halogen or amino group................FALSE

c)      In alcohol hydrogen is replaced by acyl group...............FALSE

d)      In water hydrogen is replaced by alky group or aryl group.............TRUE

e)      R group i ethers are always the same................FALSE

3.      Hydrolysis of ester leads to the formation of which of the following products in basic medium?
a) Ether and alcohol………….FALSE
b) Alcohol and sodium carboxylate…………..TRUE
c) Aldehyde and alcohol………FALSE
d) Sodium carboxylate……………..FALSE

f)       Carboxylic acid and sodium………….FALSE

4.      Chemical structure of aromatic compound is described as follows

a)      Aromatic compounds are cyclic structures in which each ring atom is a participant in a bond, resulting in delocalized electron density on both sides of the ring...............TRUE

b)       Due to this connected network of bonds, the rings are planar, unlike the boat or table structures typical of cycloalkanes...............TRUE

c)      Whenever 2 or more structures can be written for a molecule and the only difference between the structures is in the position of electrons.”…………….TRUE

d)      If two groups are attached to the benzene ring their relative position must be indicated. The three possible isomers of di-substituted benzene are differentiated by use of the names; ortho-(o) at carbon 1 & 2,meta-(m) at carbon 1 & 3 para-(p) at carbon 1 &4...................TRUE

e)      Bonds always alternate resulting to the ring becoming less reactive comparing to cyclohexene………….TRUE

 

5.      Regarding chemical properties of aromatic compounds

a)      They go through electrophilic substitution reactions and nucleophile aromatic substitution…………TRUE

b)      Hydrocarbons which have multiple bonds are unsaturated in nature like alkenes and alkynes. They tend to give addition reactions due to this unsaturation................TRUE

c)      Due to resonance and give characteristic electrophilic substitution reactions aromatic hydrocarbons are stable. The carbon ring acts as a nucleophile in these reactions and to form a substituted product an electrophile attack on benzene..............TRUE

d)      With the coming electrophile, one of the H-atom of a ring is substituted because of this the product also holds its stability and aromatic in nature.............TRUE

e)      On the opposite side in the addition reactions, aromatic compound may not lose their aromaticity, so they do not prefer to give such reactions................FALSE

 

6.      Chemical Reactions involving Ketones

a)      Most common reaction is nucleophilic addition, addition of a nucleophile and a proton across the C = O double bond...........TRUE

b)      The reactivity of the carbonyl group arises from the electro positivity of the oxygen atom and the resulting polarization of the carbon-oxygen double bond………….TRUE

c)      The electrophilic carbonyl carbon atom is sp2 hybridized and flat, leaving it relatively unhindered and open to attack from either face of the double bond…………FALSE

d)      As a nucleophile attacks the carbonyl group, the carbon atom changes hybridization from sp2 to sp3……….TRUE

e)      The electrons of the pi bond are forced out to the oxygen atom to form an alkoxide anion, which protonates to give the product of nucleophilic addition………….TRUE

 

7.      Regarding phenols

a)         Phenols are inorganic compounds which contain a hydroxyl (—OH) group attached to a carbon atom in a benzene ring..........FALSE

b)      Their chemical behaviour is very distinct from that of alcohols, because they are capable of undergoing the same oxidation reactions that alcohols participate it.............FALSE

c)      Also, unlike alcohols, phenols are weak acids, since the phenoxide anion generated by the loss of the hydroxyl proton is resonance-stabilized.............TRUE

d)      Phenol is the active ingredient in some treatments for sore throats and is found in several lozenges and throat sprays................TRUE

e)      It is used in the manufacture of many other compounds, such as aspirin, and Bakelite.........TRUE

8.      Aryl halides

a)      the compounds that contain halogen atom directly attached to the benzene ring……..TRUE

b)      They have general formula ArX……..TRUE

c)      Any halogen compound that contains a benzene ring is  classified as aryl halide………FALSE

d)      An aryl halide is classified by its distinct bonding of a halogen directly to a benzene ring………TRUE

e)      Benzyl chloride is not an aryl halide but is a substituted alkyl halide………TRUE

SECTION C: MATCHING ITEMS QUESTIONS (10 )

INSTRUCTIONS:

This section has two parts and each part has 5

Match the items from column B with those in column A by writing the letter of the correct response in the space provided on each option. USE CAPITAL LETTERS

Each correct response is awarded one (1)  

 

Column A

Column B

1. Saponification  

A.    increase the rate of electrophilic aromatic substitution, relative to hydrogen

2. Activating groups     

B.     suggests the presence of alternating single & double bonds

3.Deactivating groups        

      C.  Used to indicate that the relative position of the two substituents is 1,2−.

4. The Kekule Benzene structure   

D.    Decrease the rate of electrophilic aromatic substitution, relative to hydrogen.

5. Ortho       

      E. Used to indicate the relative positions 1,3−

 

       F. process that involves conversion of fat or oil into soap and alcohol by the action of heat in the presence of aqueous alkali (e.g. NaOH). Soaps are salts of fatty acids and fatty acids are saturated monocarboxylic acids that have long carbon chains (at least 10) e.g. CH3(CH2)14COOH.

 

Column A

1

2

3

4

5

Column B

F

A

D

B

C

 

PART B

Following are sections of the public procurement Act, 2011 which regulate procurement of medicines and medical supplies.

Match the following SECTIONS in column A with their corresponding REGULATIONS in column B by writing the letter of the correct responses in the space provided.

 

Column A

Column B

1.      Metamerism   

A.    the same formula and having different carbon chain skeletons.

2.      The IUPAC system of naming ethers 

B.     isomeric with alcohols

3.      functional isomer 

C.     alkyl alkyl ether system

4.      one of the chemical reactions of ethers   

D.    C2H5O C2H5 + 6O2 → 4CO2 + 5H2O

5.      Chain isomers  

E.     Isomers with the same molecular formula but different alkyl groups (around the functional group)

 

F.      alkoxy alkane

 

G.   

 

H.    Isomers which have the atoms of their molecules linked in a different order

 

 

 

Part A

1

2

3

4

5

Part B

E

F

B

D

A

 

 

This section consists of Four (4) questions.

Write your answers in the space provided on each question

Answer on the space provided

  1. List physical properties of Acyl chlorides ( 2mrks each)

i)       An acyl chloride like ethanoyl chloride is a colourless fuming liquid. The strong smell of ethanoyl chloride is a mixture of the smell of vinegar (ethanoic acid) and the acrid smell of hydrogen chloride gas.The smell and the fumes are because ethanoyl chloride reacts with water vapour in the air. (APPEARANCE)

 

ii)     Acyl chlorides can't be said to dissolve in water because they react (often violently) with it. The strong reaction means that it is impossible to get a simple aqueous solution of an acyl chloride.(SOLUBILITY)

 

iii)   Ethanoyl chloride boils at 51°C. (BOILING POINT)

iv)   It is a polar molecule, and so has dipole-dipole attractions between its molecules as well as van der Waals dispersion forces.However, it doesn't form hydrogen bonds.

v)       Its boiling point is therefore higher than, say, an alkane of similar size (which has no permanent dipoles), but not as high as a similarly sized alcohol (which forms hydrogen bonds in addition to everything else.)

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