Organic Chemistry Quiz | objective questions | Chemistry General Knowledge Questions | MCQ

Organic Chemistry Quiz | objective questions | Chemistry General Knowledge Questions | MCQ

1 >>IUPAC name of carbonyl chloride is: ?

• (A) Phosgene
• (B) Chloromethanoyl chloride
• (C) Dichloroketone
• (D) Dichloromethanone

Solution Its common name is phosgene and it is a poisonous gas.

2 >>How many carbons are in simplest alkyne having two side chains? ?

• (A) 5
• (B) 6
• (C) 7
• (D) 8

Solution 4 carbon chains having 2 methyl groups.

3 >>The compound name trichloroethene is: ?

• (A) Westron
• (B) Perclene
• (C) Westrosol
• (D) Orione

Solution It is the commercial name.

4 >>On evaporation of an aqueous solution of ammonium cyanate, we get urea. This is the class of reaction known as: ?

• (A) Polymerization
• (B) Isomerization
• (C) Association
• (D) Dissociation

Solution Nothing is added or eliminated, only rearrangement among atoms takes place.

5 >>Which is not found in alkenes? ?

• (A) Chain isomerism
• (B) Geometrical isomerism
• (C) Metamerism
• (D) Position isomerism

Solution Metamerism is observed when there is a change in alkyl group.

6 >>The compound C₄H₁₀O can show: ?

• (A) Metamerism
• (B) Functional isomerism
• (C) Positional isomerism
• (D) All the types

Solution This compound can be an ether which is isomeric with alcohol. Further ethers can show metamerism while alcohols can show position isomerism.

7 >>The least number of carbon atoms for an alkane to show stereoisomerism is: ?

• (A) 2
• (B) 3
• (C) 4
• (D) 5

Solution Ethane with two carbon atoms shows conformational isomerism (staggered and eclipsed isomerism).

8 >>The isomerism observed in alkanes is: ?

• (A) Metamerism
• (B) Chain isomerism
• (C) Position isomerism
• (D) Geometrical isomerism

Solution Alkanes are saturated hydrocarbons without any functional group, hence can show chain isomerism only.

9 >>The optical isomerism is shown by: ?

• (A) Oxalic acid
• (B) Benzoic acid
• (C) Acetic acid
• (D) Lactic acid

Solution Structure of lactic acid is chiral.

10 >>A similarity between optical and geometrical isomerism is: ?

• (A) Each forms equal number of isomers for a given compound
• (B) If in a compound, one is present, then so is the other
• (C) Both are included in stereoisomerism
• (D) They have no similarity

Solution Both are the types of stereoisomerism.

11 >>The number of stereoisomers possible for a compound of the molecular formula CH₃ − CH = CH − CH(OH) − Me is: ?

• (A) 3
• (B) 2
• (C) 4
• (D) 6

Solution The given compound has a C=C group and a chiral carbon.

12 >>Which of the following does not show geometrical isomerism? ?

• (A) 1,2−dichloro−1−pentene
• (B) 1,3−dichloro−2−pentene
• (C) 1,1−dichloro−1−pentene
• (D) 1,4−dichloro−2−pentene

Solution It does not show geometrical isomerism due to the presence of two similar Cl atoms on the same C atom.

13 >>Ninhydrin has 3 keto groups. Which keto group is expected to be hydrated more easily? ?

• (A) 2
• (B) 3
• (C) 1
• (D) All equally

Solution Both the −OH groups at C2 are H bonded leading to high stability of the molecule.

14 >>Bayer angle strain in cyclobutane will be: ?

• (A) 22.44^o
• (B) 90^o
• (C) 9.4^o
• (D) 0.44^o

Solution (109.5 − 90) ⁄ 2 = 9.4

15 >>Which of the following is a true statement? ?

• (A) RCOOH is more stable than RCOO⁻
• (B) RCOO⁻ is more stable than RCOOH
• (C) RCOO⁻ and RCOOH do not show resonating structures
• (D) All of the above

Solution This is due to resonance.

16 >>The electron attracting species in the following are: ?

• (A) −CN
• (B) −NH₂
• (C) −NHR
• (D) −NHCOR

Solution The groups having double or triple bonds are electron attracting.

17 >>pK_a values of HCN, CH₃COOH and HF respectively are 9.2, 4.7 and 3.2. Evaluate pK_b for CN⁻, CH₃COO⁻ and F⁻. ?

• (A) 9.2, 4.7, 16.0
• (B) 4.8, 9.3, 10.8
• (C) 7.2, 3.7, 3.2
• (D) 2.2, 2.3, 3.8

Solution pKa + pKb = 14

18 >>2,3−dibromobutane, when heated with zinc dust yields: ?

• (A) 2−butene
• (B) 2−butyne
• (C) 1−butane
• (D) Butane

Solution Heating with zinc dust brings about dehalogenation of 2,3−dibromobutane.

19 >>2−pentyne can be converted into trans−pent−2−ene by reaction with: ?

• (A) H₂⁄Ni
• (B) H₂⁄Lindlar′s catalyst
• (C) Na⁄liq. NH₃
• (D) Zn⁄HCl

Solution Sodium in the presence of liquid ammonia converts alkynes to corresponding trans−alkenes.

20 >>Which of the following compounds has the highest melting point? ?

• (A) n−butane
• (B) n−pentane
• (C) n−hexane
• (D) n−heptane

Solution n−heptane has the longest chain of carbon atoms.

21 >>Which of the following compounds has the highest boiling point? ?

• (A) Ethene
• (B) Propene
• (C) cis−2−butene
• (D) trans−2−butene

Solution cis−isomer has higher boiling point than trans due to its greater polarity.

22 >>The reaction of toluene with Cl₂ in presence of FeCl₃ gives predominantly: ?

• (A) m−chlorobenzene
• (B) Benzoyl chloride
• (C) Benzyl chloride
• (D) o− and p−chlorotoluene

Solution In presence of FeCl3 (Lewis acid), side chain hydrogen atoms of toluene are substituted.

23 >>Which one of the following conformations of cyclohexane is chiral? ?

• (A) Boat
• (B) Twist boat
• (C) Rigid
• (D) Chair

Solution Chiral conformation will not have a plane of symmetry.

24 >>Octane number can be changed by: ?

• (A) Isomerization
• (B) Alkylation
• (C) Cyclisation
• (D) All of these

Solution Octane number can be increased by all of these.

25 >>An unknown compound A has the formula C₄H₆. When A is treated with excess of Br₂, a new compound B is formed with formula C₄H₆Br₄. A also gives white ppt. with Tollen′s reagent. The compound A may be: ?

• (A) But−1−yne
• (B) But−2−yne
• (C) But−1−ene
• (D) But−2−ene

Solution The data suggests that compound A is a terminal alkyne.

26 >>Xylene on treatment with Br₂⁄FeBr₃ gives only one product. Xylene was: ?

• (A) o−xylene
• (B) m−xylene
• (C) p−xylene
• (D) Not possible

Solution In p−xylene, all the positions are equivalent and give only one monosubstituted product.

27 >>The name fire damp is given to: ?

• (A) Methane
• (B) Ethane
• (C) Propane
• (D) Butane

Solution Methane is found in coal mines where it forms an explosive mixture with air and is thus, known as fire damp.

28 >>In which of the following compounds, addition of HBr in presence and absence of peroxide will have no effect? ?

• (A) 1−butene
• (B) 2−butene
• (C) Isobutene
• (D) 2−pentene

Solution Markownikov and anti Markownikov addition is applicable only on asymmetrical alkenes, so, 2−butene being a symmetrical alkene would give the same product in both the cases.

29 >>Anti Markownikov′s addition of HBr is not observed in: ?

• (A) Propene
• (B) But−1−ene
• (C) But−2−ene
• (D) Pent−3−ene

Solution Not observed in symmetrical alkenes.

30 >>18 C−H and 7 C−C sigma bonds are present in: ?

• (A) n−heptane
• (B) Cyclohexane
• (C) 3,3−dimethyl pentane
• (D) 2,2,3−trimethyl pentane

Solution Number of C−C sigma bonds = Number of carbons − 1 and Number of C−H sigma bonds = Number of hydrogens

31 >>Periodic acid oxidises: ?

• (A) 1,4−diols
• (B) 1,3−diols
• (C) 1,2−diols
• (D) β−ketoaldehyde

Solution Periodic acid is specific for 1,2−diol splitting.

32 >>Which of the following is the most suitable method for removing the traces of water from ethanol? ?

• (A) Heating with sodium metal
• (B) Passing dry HCl gas through it
• (C) Distilling it
• (D) Reacting with Mg

Solution Magnesium first reacts with ethanol to form magnesium ethoxide, which then reacts with water to regenerate ethanol along with magnesium hydroxide.

33 >>Oxymercuration−demercuration reaction of 1−methyl cyclohexene gives: ?

• (A) trans−2−methyl cyclohexanol
• (B) cis−2−methyl cycloheaxanol
• (C) 1−methyl cyclohexanol
• (D) Mixture of cis− and trans−2−methyl cyclohexanol

Solution During oxymercuration−demercuration reactions, products corresponding to Markownikov′s addition of H2O are formed.

34 >>The function of ZnCl₂ in Lucas test for alcohols is: ?

• (A) To act as acid catalyst and react with HCl to form H₂ZnCl₄
• (B) To act as base catalyst and react with NaOH to form Na₂Zn(OH)₄
• (C) To act as amphoteric catalyst
• (D) To act as neutral catalyst

Solution In presence of anhydrous ZnCl2, alcohol reacts with conc. HCl to produce alkyl chloride.

35 >>In water, H−O−H bond angle is 104.5^o, but in ethers (R−O−R), the C−O−C bond angle is about 110^o. The reason to justify it, is: ?

• (A) Positive inductive effect of alkyl groups is more than that of hydrogen
• (B) The alkyl group is polar, while hydrogen is not
• (C) Distortion caused by the lone pair of oxygen atom is more than compensated by the bulky alkyl groups
• (D) The hybridisation of oxygen atoms is different in ethers and in water

Solution Bulky groups counter balance the repulsion caused by the lone pairs.

36 >>An aromatic ether is not cleaved by HI even at 525 K. The aromatic ether is: ?

• (A) C₆H₅OCH₃
• (B) C₆H₅OC₆H₅
• (C) C₆H₅OC₃H₇
• (D) Tetrahydrofurane

Solution Due to greater electronegativity of sp2 hybridised carbon atoms of the benzene ring, dialkyl ethers are not attacked by nucleophiles like I−.

37 >>In a reaction, RCHO is reduced to RCH₃ using amalgamated zinc and conc. HCl, and warming the solution. The reaction is known as: ?

• (A) Meerwein−Ponddorf reaction
• (B) Clemmensen reaction
• (C) Wolff−Kishner reaction
• (D) Schiff reaction

Solution In Clemmensen reduction, aldyhydes and ketones are reduced into hydrocarbons.

38 >>The most reactive compound towards formation of cyanohydrin on treatment with KCN followed by acidification is: ?

• (A) p−nitrobenzaldehyde
• (B) p−hydroxybenzaldehyde
• (C) Benzaldehyde
• (D) Phenylacetaldehyde

Solution Due to electron withdrawing nature of NO2 group, the partial positive charge on the carbon atom of the C=O group in p−nitrobenzaldehyde increases and becomes more susceptible to nucleophilic attack by CN− group.

39 >>A mixture of benzaldehyde and formaldehyde on heating with aqueous NaOH solution gives: ?

• (A) Benzyl alcohol and sodium formate
• (B) Sodium benzoate and methyl alcohol
• (C) Sodium benzoate and sodium formate
• (D) Benzyl alcohol and methyl alcohol

Solution It is a cross−Cannizaro reaction.

40 >>The correct order of acidic strengths of the carboxylic acids is: ?

• (A) Formic acid < Benzoic acid < Acetic acid
• (B) Formic acid < Acetic acid < Benzoic acid
• (C) Acetic acid < Formic acid < Benzoic acid
• (D) Acetic acid < Formic acid < Benzoic acid

Solution Acidic strength is the tendency to give H+ ions.

41 >>The heat of hydrogenation of benzene is 50 kcal⁄mol. The resonance energy of benzene is 36 kcal⁄mol. The heat of hydrogenation of cyclohexene is approximately: ?

• (A) 9 kcal⁄mol
• (B) 19 kcal⁄mol
• (C) 29 kcal⁄mol
• (D) 27 kcal⁄mol

Solution c

42 >>Elimination of bromine from 2−bromobutane results in the formation of: ?

• (A) Equimolar mixture of 1− and 2−butene
• (B) Predominantly 2−butene
• (C) Predominantly 1−butene
• (D) Predominantly 2−butyne

Solution b

43 >>Electrolysis of cold concentrated aqueous solution of potassium succinate yields: ?

• (A) Ethane
• (B) Ethyne
• (C) Ethene
• (D) Ethane−1,2−diol

Solution c

44 >>1,2−dibromopropane on treatment with X moles of NaNH₂ followed by treatment with ethyl bromide gave pentyne. The value of X is: ?

• (A) 1
• (B) 2
• (C) 3
• (D) 4

Solution c

45 >>When acetylene reacts with arsenic trichloride in the presence of anhydrous aluminium chloride, it produces: ?

• (A) β−chlorovinyldichloroarsine
• (B) Lewisite
• (C) Nitrobenzene
• (D) Both (1) and (2)

Solution d

46 >>Which of the following will undergo metasubstitution on monochlorination? ?

• (A) Ethoxybenzene
• (B) Chlorobenzene
• (C) Ethylbenzoate
• (D) Phenol

Solution c

47 >>The reaction of cis−2−butene with CH₂I₂ and Zn (Cu) to give cis−1,2−dimethyl cyclopropane is: ?

• (A) Stereospecific reaction
• (B) Enantiospecific reaction
• (C) Diastereoselective reaction
• (D) Regioselective reaction

Solution a

48 >>2−methylbutane on reacting with bromine in the presence of sunlight gives mainly: ?

• (A) 1−bromo−3−methylbutane
• (B) 2−bromo−3−methylbutane
• (C) 2−bromo−2−methylbutane
• (D) 1−bromo−2−methylbutane

Solution c

49 >>Acid catalysed hydration of alkenes except ethene leads to the formation of: ?

• (A) Mixture of secondary and tertiary alcohols
• (B) Mixture of primary and secondary alcohols
• (C) Secondary or tertiary alcohol
• (D) Primary alcohol

Solution c

50 >>Benzene hexachloride is prepared from benzene and chlorine in sunlight by: ?

• (A) Subsitution reaction
• (B) Elimination reaction
• (C) Addition reaction
• (D) Rearrangement

Solution c

51 >>Reaction of t−butyl bromide with sodium methoxide produces: ?

• (A) Isobutane
• (B) Isobutylene
• (C) Sodium t−butoxide
• (D) t−butyl methyl ether

Solution b

52 >>One of the following that can not undergo dehydrohalogenation is: ?

• (A) Iso−propyl bromide
• (B) Ethanol
• (C) Ethyl bromide
• (D) None of these

Solution b

53 >>Which of the following statements is true when (CCl₃)₃−OH reacts with Lucas reagent? ?

• (A) Cloudiness appears immediately
• (B) Cloudiness appears within 10 minutes
• (C) Cloudiness will not appear at room temperature
• (D) Ketone will be formed in this reaction

Solution c

54 >>Ether is obtained by the reaction of ethyl alcohol and H₂SO₄ at: ?

• (A) 474 K
• (B) 383 K
• (C) 413 K
• (D) 273 K

Solution c

55 >>The correct order of increasing boiling points is: ?

• (A) Isobutane < n−butane < n−butyl chloride < n−butanol
• (B) Isobutane < n−butyl chloride < n−butane < n−butanol
• (C) n−butane < n−butanol < n−butyl chloride < isobutane
• (D) n−butane < isobutane < n−butyl chloride < n−butanol

Solution a

56 >>The reaction of HCOOH with conc. H_{SO4 gives: ?}

• (A) CO₂
• (B) CO
• (C) Oxalic acid
• (D) Acetic acid

Solution b

57 >>Alkaline or acid hydrolysis of CH₃COCl is nothing but: ?

• (A) Electrophilic substitution
• (B) Nucleophilic substitution
• (C) Free radical substitution
• (D) Biradical substitution

Solution b

58 >>An organic compound gives a fruity smell. The compound on distillation in presence of dilute alkali yields a product capable of giving positive iodoform test. The compound is: ?

• (A) Methyl formate
• (B) Isopropyl acetate
• (C) Methyl propionate
• (D) n−propyl formate

Solution b

59 >>Acetic acid exists as dimer in C₆H₆ due to: ?

• (A) Condensation reaction
• (B) Hydrogen bonding
• (C) Presence of a carboxyl group
• (D) Presence of hydrogen at α−carbon

Solution b

60 >>Which of the following lacks chirality? ?

• (A) 2−hydroxy propanoic acid
• (B) 2−amino propanoic acid
• (C) 2,3−butene−dioic acid
• (D) 2,3−dihydroxy butanoic acid

Solution c