Chemistry

Chemical Reactions and Equations

684 Questions

Chemical reactions and equations form a foundational chemistry topic where students identify reaction products, balance chemical formulas, and classify reaction types. It covers critical mechanisms like Markovnikov's rule, precipitation, and endothermic or exothermic processes. These questions are highly common in general science sections of state and central government competitive exams.

Endothermic reactionsPrecipitation reactionsDehydrohalogenation of alkyl halidesChemical equation balancingReaction product identification

Chemical Reactions and Equations Questions

Multiple choice

Among the following -------------------- reagent acts as a catalyst in the production of polyurethane.

  1. Tetramethylguanidine

  2. 2,2,6,6-Tetramethylpiperidine

  3. 2,2,2-Trichlorethoxycarbonyl chloride

  4. 1,3-Propanedithiol
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Tetramethylguanidine is a strong amine base with a higher pKa than typical amines, therefore it can be used where a higher pKa is needed and as a substitute for DBU, DBN. It is also used as a catalyst in the production of polyurethane.

Multiple choice

The reagent used for adding water to a terminal alkyne is

  1. Azobisisobutyronitrile

  2. 2,2'-Dipyridyldisulphide

  3. Disiamylborane

  4. Eschenmoser's salt
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Disiamylborane is an organoborane used in organic synthesis to add water to a terminal alkyne, forming an aldehyde via anti-Markovnikov addition. Disiamylborane is relatively unreactive and will not react with triple-bonded carbons that are not at the terminal position.

Multiple choice

Among the following reagents ____________ is used in radical substitution and electrophilic addition reactions.

  1. n-Bromosuccinimide

  2. tert-Butanesulphinamide

  3. tert-Butyl hydroperoxide

  4. fluorenylmethyloxycarbonyl chloride
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

N-Bromosuccinimide or NBS is a chemical reagent which is used in radical substitution and electrophilic addition reactions in organic chemistry. NBS can be considered a convenient source of cationic bromine.

Multiple choice

The reagent used in Perkin synthesis is

  1. n-Butyllithium

  2. tert-Butyllithium

  3. Caesium acetate

  4. Carbon tetraiodide
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Caesium acetate is an ionic caesium compound often used in organic synthesis especially in Perkin synthesis; formation of unsaturated cinnamic-type acids by the condensation of aromatic aldehydes with fatty acids.

Multiple choice

The reagent used as a catalyst and complexing ligand in the organic reactions is

  1. 1,8-Diazabicyclo[5.4.0]undec-7-ene

  2. Dibutylboron trifluoromethanesulphonate

  3. Dichloromethyl methyl ether

  4. Diethyl azodicarboxylate
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

1,8-Diazabicyclo[5.4.0]undec-7-ene or more commonly DBU, is a chemical compound and belongs to the class of amidine compounds. It is used in organic synthesis as a catalyst and complexing ligand and a strong (pKa = 24.34 in acetonitrile) non-nucleophilic base.

Multiple choice

Which of the following acts as a nucleophilic catalyst in organic reactions?

  1. Dimethyl malonate

  2. Diethyl malonate

  3. 4-Dimethylaminopyridine

  4. Dimethyldioxirane
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

4-Dimethylaminopyridine is a derivative of pyridine. This colourless solid is a useful nucleophilic catalyst for a variety of reactions such as esterifications with anhydrides, the Baylis-Hillman reaction, hydrosilylations, tritylation, the Steglich rearrangement, Staudinger synthesis of β-lactams and many more. vv

Multiple choice

Which of the following reagents is used in acidic modification of the Hofmann rearrangement?

  1. Bis(chloromethyl) ether

  2. (Bis(trifluoroacetoxy)iodo)benzene

  3. Bis(trimethylsilyl)acetamide

  4. Bis(trimethylsilyl)amine
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

(Bis(trifluoroacetoxy)iodo)benzene is a hypervalent iodine compound used as a reagent in organic chemistry. The reagent is used in an acidic modification of the Hofmann rearrangement. One example is the conversion of cyclobutanecarboxamine to cyclobutylamine hydrochloride.

Multiple choice

Pseudo-pericyclic reactions are reactions that appear at first glance to be pericyclic.Which of the following reaction is 'pseudo' pericyclic?

  1. Transmetalation

  2. Carbometalation

  3. Hydrometalation

  4. Alkyne trimerisation
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

An alkyne trimerisation reaction is a 2+2+2 cyclisation reaction in which three alkyne molecules react to form an aromatic compound. The reaction is 'pseudo' pericyclic since it has not been observed to occur without the assistance of metal catalysis; and the metal catalyst assembles the ring stepwise via intermediates which are not directly in between (in a geometric sense) the starting material and products.

Multiple choice

Assertion: The compound C6H5CH=CHCl is called β-chlorostyrene. Reason: In organic halides, the carbon atom attached to the halogen atom designated as α.

  1. Both A and R are true and R is the correct explanation of A.

  2. Both A and R are true but R is NOT the correct explanation of A.

  3. A is true but R is false.

  4. A is false but R is true.

  5. Both A and R are false.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

This option is correct, because in styrene, carbon atom attached to phenyl group is designated as α-carbon while that carrying Cl-atom is designated as β-carbon.

Multiple choice

Assertion: Benzaldehyde forms two oximes on reacting with NH2OH. Reason: The two oximes arise due to geometrical isomerism around C=N bond.

  1. Both A and R are true and R is the correct explanation of A.

  2. Both A and R are true but R is NOT the correct explanation of A.

  3. A is true but R is false.

  4. A is false but R is true.

  5. Both A and R are false.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Benzaldehyde forms two oximes on reacting with NH2OH because the two oximes arise due to geometrical isomerism around C=N bond. Thus, this option is correct.

Multiple choice

Which of the following process describes the exchange of ligands between two metal centers?

  1. Oxidative addition

  2. Beta-hydride elimination

  3. Transmetalation

  4. Carbometalation
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Transmetalation is a general chemical reaction type in organometallic chemistry describing the exchange of ligands between two metal centers. The metal centers need not be the same. The ligands R and R' can be organic or inorganic. The double displacement reaction is conceptually related. Transmetalation is important in the synthesis of various organometallic compounds.

Multiple choice

Assertion: Friedel-Crafts reaction between benzene and acetic anhydride in the presence of anhydrous AlCl3 yield. Reason: Acetophenone formed poisons the catalyst preventing further reaction.

  1. Both A and R are true and R is the correct explanation of A.

  2. Both A and R are true but R is NOT the correct explanation of A.

  3. A is true but R is false.

  4. A is false but R is true.

  5. Both A and R are false.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

This option is correct because CH3CO group in acetophenone being electron withdrawing reduces the electron density in the benzene ring-thereby preventing further electrophilic substitution.

Multiple choice

Which of the following statements is/are incorrect? A. Corey-House reaction can be used to prepare only alkenes with odd number of carbon atoms. B. Reforming involves conversion of aliphatic into aromatic hydrocarbons. C. The formation of alkenes by the action of zinc on alkyl halides is called Frankland reaction.

  1. Only A

  2. Only B

  3. Only C

  4. A and C

  5. A, B and C
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

This option is correct,  because Corey-House reaction can be used to prepare both alkenes with odd and even number of carbon atoms.