300+ REAL TIME Organic Chemistry Objective Questions & Answers 2023

250+ TOP MCQs on Transesterification and Answers

Organic Chemistry Multiple Choice Questions on “Transesterification”.

1. Which of the following is true about transesterification?
a) exchanging the organic alkyl group of an ester with the organic group alkyl of an alcohol
b) exchanging the organic alkyl group of an alcohol with the organic group alkyl of an ester
c) exchanging the organic alkyl group of an ester with the organic group alkyl of an alkane
d) exchanging the organic alkyl group of an ester with the organic group alkyl of an ether
Answer: a
Clarification: Transesterification is the process of exchanging the organic group R″ of an ester with the organic group R′ of an alcohol.

2. What is the geometry of the intermediate formed in the mechanism of transesterification?
a) Octahedral
b) Square planner
c) Tetrahedral
d) Square bipyramidal
Answer: c
Clarification: In the transesterification mechanism, the carbonyl carbon of the starting ester reacts to give a tetrahedral intermediate, which either reverts to the starting material, or proceeds to the transesterified product.

3. What chemical reaction makes biodiesel?
a) Transesterification
b) Sublimation
c) Polymerization
d) Fermentation
Answer: a
Clarification: Transesterification chemical reaction makes biodiesel. The most common method of transesterification is the reaction of the ester with an alcohol in the presence of an acid catalyst.

4. Polyethylene terephthalate is prepared by a transesterification reaction.
a) True
b) False
Answer: a
Clarification: By transesterification reaction between dimethyl terephthalate and the dihydric alcohol, ethylene glycol, polyethylene terephthalate is prepared along with methanol, which is evaporated to drive the reaction forward.

5. What type of solution is used in transesterification for the determination of fatty acid compositions?
a) Methanol in NaOH
b) Methanol in NaCl
c) Methanol in KOH
d) Methanol in H₂O
Answer: a
Clarification: In aqueous warm solution of methanol in NaOH esterification for the determination of fatty acid compositions.

6. Transesterification reaction is an irreversible reaction.
a) True
b) False
Answer: b
Clarification: The most common method of transesterification is the reaction of the ester with an alcohol in the presence of an acid catalyst. Since both the reactants and the products are an ester and an alcohol, the reaction is reversible and the equilibrium constant is close to one.

7. Which of the following is the product formed when methyl ethanoate and ethanol in presence of hydrochloric acid?
a) Ethyl ethanoate
b) Methyl ethanoate
c) Ethyl propanoate
d) Propyl ethanoate
Answer: a
Clarification: Methyl ethanoate reacts with ethanol in the presence of hydrochloric acid to form ethyl ethanoate and methanol.

8. Which of the following is the product formed when alkylene carbonate and alcohol in presence of hydrochloric acid?
a) Dialkyl carbonate
b) Methyl ethanoate
c) Alkyl carbonate
d) Propyl ethanoate
Answer: a
Clarification: The transesterification reaction implies an alkylene or cyclic carbonate and an alcohol in the presence of either a homogeneous or heterogeneous acidic or basic catalyst to coproduce dialkyl carbonate and the alkane diol or glycol.

9. Which of the following is the product formed when methyl propanoate and ethanol in presence of hydrochloric acid?
a) Ethyl ethanoate
b) Methyl ethanoate
c) Ethyl propanoate
d) Propyl ethanoate
Answer: c
Clarification: Methyl propanoate reacts with ethanol in the presence of hydrochloric acid to form ethyl propanoate and methanol.

10. Which of the following is the product formed when butyl acetate and ethanol in presence of hydrochloric acid?
a) Ethyl ethanoate
b) Methyl acetate
c) Ethyl acetate
d) Propyl ethanoate
Answer: c
Clarification: Butyl acetate reacts with ethanol in the presence of hydrochloric acid to form ethyl acetate and butanol.

250+ TOP MCQs on Polarimeter and Answers

Organic Chemistry Multiple Choice Questions on “Polarimeter”.

1. What does a polarimeter measure?
a) Polarity of the substance
b) Angle of rotation of an optical active compound
c) Concentration of the substance
d) pH of the substance
Answer: b
Clarification: A polarimeter is a scientific instrument used to measure the angle of rotation caused by passing polarized light through an optically active substance.

2. A solution of 0.1 g/mL of a pure R enantiomer in a 1.0 dm (i.e., 10 cm) polarimeter rotates plane polarized light by +4.8°. What is the rotation observed on this solution in a 2 dm polarimeter?
a) +2.4°
b) +4.8°
c) +19°
d) +9.6°
Answer: d
Clarification: The specific optical rotation of a sample, [α], is calculated using the equation [α] = α/cl, where α is the observed rotation, c is the concentration (in g/mL), and l is the pathlength (in dm). [α] is a constant for a sample.

3. Polarimeter works on the principle of which of the following?
a) polarisation of light
b) change of the electrical conductivity of solution with composition
c) change of angle of refraction with composition
d) change of electrical conductivity of solution with temperature
Answer: a
Clarification: If light encounters a polarizer, only the part of the light that oscillates in the defined plane of the polarizer may pass through. That plane is called the plane of polarization. The plane of polarization is turned by optically active compounds. According to the direction in which the light is rotated, the enantiomer is referred to as dextro-rotatory or levo-rotatory.

4. What is the effect of the I on the specific optical rotation (α), if I gets double?
a) α gets double
b) α gets halved
c) α gets four times
d) α eight times
Answer: a
Clarification: Specific rotation, [α], is a fundamental property of chiral substances that is expressed as the angle to which the material causes polarized light to rotate at a particular temperature, wavelength, and concentration. Doubling l will double the value of α.

5. If a solution of a compound (30.0 g/100 mL of solution) has a measured rotation of +15° in a 2 dm tube, what is the specific rotation?
a) +50°
b) +25°
c) +15°
d) +7.5°
Answer: b
Clarification: The specific optical rotation of a sample, [α], is calculated using the equation [α] = α/cl, where α is the observed rotation, c is the concentration (in g/mL), and l is the pathlength (in dm). [α] is a constant for a sample.

6. Which of the following groups has the highest priority according to the Cahn-Ingold-Prelog sequence rules?
a) CH₃
b) CH₂Cl
c) CH₂OH
d) CHO
Answer: b
Clarification: R/S and E/Z descriptors are assigned by using a system for ranking priority of the groups attached to each stereocenter. This procedure, often known as the sequence rules, is the heart of the CIP system. Compare the atomic number (Z) of the atoms directly attached to the stereocenter; the group having the atom of higher atomic number receives higher priority.

7. What is the percent composition of a mixture of (S)-(+)-2-butanol, α= +13.52°, and (R)-(-)-2-butanol, α = -13.52°, with a specific rotation α = +6.76°?
a) 75%(R) 25%(S)
b) 25%(R) 75%(S)
c) 50%(R) 50%(S)
d) 67%(R) 33%(S)
Answer: b
Clarification: The specific optical rotation of a sample, [α], is calculated using the equation [α] = α/cl, where α is the observed rotation, c is the concentration (in g/mL), and l is the pathlength (in dm). [α] is a constant for a sample.

8. What can be said with certainty if a compound has α= -9.25°?
a) The compound has the (S) configuration
b) The compound has the (R) configuration
c) The compound is not a meso form
d) The compound possesses only one stereogenic center
Answer: c
Clarification: Compounds which rotate the plane of polarization of plane polarized light counterclockwise are said to be levorotary and correspond with negative values. It is optically active substance.

9. Which of these is a comparatively insignificant factor affecting the magnitude of specific optical rotation?
a) Concentration of the substance of interest
b) Purity of the sample
c) Temperature of the measurement
d) Length of the sample tube
Answer: c
Clarification: The specific rotation of a molecule is the rotation in degrees observed upon passing polarized light through a path length of 1 decimetre (dm) at a concentration of 1 g/mL. Specific rotation is almost always reported along with the temperature, wavelength of light used, the solvent, and the concentration, since it is sensitive to these factors as well.

10. What is the specific optical rotation of (S)-malic acid at a concentration of 5.5 g/ mL in the solvent pyridine at 20°C at a wavelength of 589 nm?
a) the specific rotation is –27°
b) the specific rotation is +27°
c) the specific rotation is –17°
d) the specific rotation is +17°
Answer: a
Clarification: The specific optical rotation of a sample, [α], is calculated using the equation given below, α (is the measured rotation in degrees, l is the path length in decimeters, and ρ (Greek letter “rho”) is the concentration of the liquid in g/mL, for a sample at a temperature T (given in degrees Celsius) and wavelength λ (in nanometers).

250+ TOP MCQs on Coordination Polymerisation and Answers

Organic Chemistry Problems on “Coordination Polymerisation”.

1. Which of the following is true about coordination polymerisation?
a) radical, coordination, anionic, or cationic polymerization, depending on the type of initiation
b) polymerization that is catalysed by transition metal salts and complexes
c) monomers react by eliminating small molecules like H₂O, NH₃, CH₂O and NaCl in a repetitive manner, Indefinite growth of the polymer occurs at both ends
d) a mixture of more than one (or different) monomeric species is allowed to polymerize
Answer: b
Clarification: Coordination polymerisation is a form of polymerization that is catalysed by transition metal salts and complexes. In this addition of monomer to a metal complex take place, followed by propagation is by successive insertion of monomer at the metal, and termination occurs when the metal complex separates from the polymer.

2. Which catalyst is commonly used in coordination chain polymerization?
a) nickel
b) ziegler- Natta catalyst
c) zeolite
d) platinum
Answer: b
Clarification: A Ziegler–Natta catalyst, named after Karl Ziegler and Giulio Natta, is a catalyst used in the synthesis of polymers of 1-alkenes (alpha-olefins).

3. Which of the following is true about homogenous Ziegler Natta polymerisation?
a) This is based on titanium tetrachloride organoaluminium co-catalyst
b) This is based on Kaminsky catalyst
c) This is based on neodymium-based catalyst
d) This is based on organoaluminium co-catalyst
Answer: b
Clarification: The Homogenous Ziegler Natta coordination polymerization is done with the help of homogenous catalyst such as the Kaminsky catalyst. Kaminsky catalysts are based on metallocenes of group 4 metals (Ti, Zr, Hf) activated with methylaluminoxane (MAO).

4. Which of the following olefine undergo coordination polymerisation in the presence of Ziegler-Natta catalysts?
a) vinyl chloride
b) vinyl ethers
c) acrylate esters
d) ethylene
Answer: d
Clarification: The mixing of TiCl₄ with trialkylaluminium complexes produces Ti(III)-containing solids that catalyze the polymerization of ethylene. Many alkenes do not polymerize in the presence of Ziegler-Natta or Kaminsky catalysts. This problem applies to polar olefins such as vinyl chloride, vinyl ethers, and acrylate esters.

5. Which of the following is true about heterogeneous Ziegler Natta polymerisation?
a) This is based on titanium tetrachloride
b) This is based on Kaminsky catalyst
c) This is based on neodymium-based catalyst
d) This is based on titanium tetrachloride organo-aluminium co-catalyst
Answer: d
Clarification: Coordination polymerization with heterogeneous Ziegler-Natta catalysts is based on titanium tetrachloride and organoaluminium co-catalyst. The mixing of TiCl₄ with trialkylaluminium complexes produces Ti(III)-containing solids that catalyse the polymerization of ethylene and propylene.

6. Homogenous Ziegler Natta coordination polymerization occurs via which mechanism?
a) Cossee–Arlman mechanism
b) Mechanism of free-radical polymerization
c) Cationic polymerization mechanism
d) Anionic polymerization mechanism
Answer: a
Clarification: The Cossee–Arlman mechanism is the pathway for the formation of C–C bonds in the polymerization of alkenes. The mechanism features an intermediate coordination complex that contains both the growing polymer chain and the monomer (alkene), these ligands combine within the coordination sphere of the metal to form a polymer chain that is elongated by two carbons.

7. Which catalyst is used for the coordination polymerisation of polybutadiene?
a) titanium tetrachloride organo-aluminium co-catalyst
b) kaminsky catalyst
c) neodymium-based catalyst
d) organo-aluminium co-catalyst
Answer: c
Clarification: The salt of neodymium has been widely used in industrial polymerization of 1,3-butadiene. The neodymium catalyst causes high catalytic activity during the polymerization of dienes, however good control has not been achieved with regard to molecular weight and molecular weight distribution.

8. Titanium tetrachloride organoaluminium co-catalyst is used in which of the following polymerisation?
a) Ziegler-Natta polymerization
b) Anionic vinyl polymerization
c) Free-radical polymerization
d) Metathesis polymerization
Answer: a
Clarification: Coordination polymerization with heterogeneous Ziegler-Natta catalysts is based on titanium tetrachloride and organo-aluminium co-catalyst. The mixing of TiCl₄ with trialkylaluminium complexes produces Ti(III)-containing solids that catalyse the polymerization of ethylene and propylene.

Organic Chemistry Problems,