Question 1

Synthesis of alkanes from alkyl halides is a typical example of E2 reaction.

Accepted Answer

Synthesis of alkanes from alkyl halides is typically achieved through substitution reactions, such as SN1 or SN2, rather than elimination reactions like E2.

Question 2

Electrophilic substitution reactions are typical reactions of aromatic compounds.

Accepted Answer

Electrophilic substitution reactions involve the attack of an electrophile on the delocalized pi electrons of an aromatic compound, leading to the formation of a substituted product.

Question 3

Find the combination of conditions that are the best for S_N2 reactions. A)The substrate is a tertiary alkyl iodide,solvent is aprotic,polar and the nucleophile is a strong base. B)The substrate is a primary alkyl iodide,solvent is aprotic,polar and the nucleophile is a strong base. C)The substrate is a primary alkyl fluoride,solvent is protic,polar and the nucleophile is a strong base. D)The substrate is a primary alkyl iodide,solvent is non-polar and the nucleophile is a weak base. E)The substrate is a tertiary alkyl iodide,solvent is non-polar and the nucleophile is a strong base.

Accepted Answer

The correct notation for the reaction type seems to be a mix-up. Assuming it refers to SN1 and SN2 reactions: SN2 reactions are favored by primary alkyl halides, aprotic polar solvents, and strong nucleophiles, which matches option B.

Question 4

The step reaction polymerizations are fast polymerization reactions.

Accepted Answer

Step reaction polymerizations, also known as condensation polymerizations, typically proceed at a slower rate compared to chain growth polymerizations because they involve the gradual reaction of functional groups, often with the elimination of small molecules like water, and require the diffusion of larger and larger molecules as the polymer grows.

Question 5

Which of the following trends in nucleophilicity are correct?
I.Everything else being equal,a negatively charged nucleophile will react faster than a neutral one.
II.Generally,species containing elements of high electronegativity are good nucleophiles.
III.Anionic nucleophiles are more reactive in polar and aprotic solvents than in polar and protic solvents.
IV.Generally,nucleophilicity is increasing with the increase in size of an atom.
V.Bulky groups adjacent to the nucleophilic atom enhance the nucleophilicity and reactivity of the species.
A)I,II,III,and V
B)II,III,IV and V
C)I,II and IV
D)II,III and V
E)III,IV and V

Accepted Answer

Explanation:I. True, because the negative charge on the nucleophile makes it more reactive.II. False, because species containing elements of high electronegativity are poor nucleophiles.III. True, because anionic nucleophiles are more reactive in polar and aprotic solvents than in polar and protic solvents.IV. False, because nucleophilicity is generally decreasing with the increase in size of an atom.V. False, because bulky groups adjacent to the nucleophilic atom hinder the nucleophilic attack and decrease the reactivity of the species.

Question 6

The alkanes are known for their reactivity.

Accepted Answer

The alkanes are known for their low reactivity due to their strong carbon-carbon and carbon-hydrogen covalent bonds. They only undergo limited reactions, such as combustion and halogenation, under specific conditions.

Question 7

Which of the following steps can be found in E1 reaction mechanism?
I.formation of a carbocation
II.attack of the base and removal of a proton from carbocation
III.attack of a nucleophile
IV.formation of a carboanion
A)I and II
B)only II
C)I and III
D)III and IV
E)only III

Accepted Answer

In an E1 reaction, the first step involves the formation of a carbocation (I). This is followed by attack of the base and removal of a proton from the carbocation (II). Formation of a carboanion (IV) is not a step in E1 reaction, whereas attack of a nucleophile (III) is a step in SN1 reaction. Therefore, only steps I and II are found in E1 reaction mechanism.

Question 8

Nucleophiles are electron poor atoms,ions or groups.

Accepted Answer

Nucleophiles are electron rich atoms, ions or groups that are attracted to positively charged atoms or molecules.

Question 9

Which of the following statements correctly describe S_N2 and S_N1 reactions? I.S_N2 reactions proceed with retention of configuration. II.S_N1 reactions prefer polar protic solvents. III.S_N1 reactions can produce racemic products. IV.S_N2 reactions are promoted in the presence of a substrate that produces a very stable carbocation. V.S_N1 reactions have a unimolecular rate-determining step. A)I,IIand V. B)II,III,and IV. C)III,IV and V. D)II,IIIand V. E)I,III,and IV.

Accepted Answer

S_N2 reactions proceed with retention of configuration (I), but this is not mentioned for S_N1 reactions. S_N1 reactions can produce racemic products (III), and this is not mentioned for S_N2 reactions. S_N1 reactions prefer polar protic solvents (II), while this is not mentioned for S_N2 reactions. S_N2 reactions are promoted in the presence of a substrate that produces a very stable carbocation (IV), but this is not mentioned for S_N1 reactions. Finally, S_N1 reactions have a unimolecular rate-determining step (V), while this is not mentioned for S_N2 reactions. Therefore, the correct answer is D (II, III, and V).

Question 10

S_N2 reactions are nucleophilic substitution reactions for which the rate determining step is bimolecular.

Accepted Answer

The term S_N2 refers to a specific type of nucleophilic substitution reaction where the rate determining step involves two molecules coming together. This is known as a bimolecular rate determining step, and it is typically faster than a unimolecular rate determining step. Therefore, the statement is true.

Question 11

The following can be said about the reaction profile of an S_N1 reaction: I.The rate determining step is the formation of a carbocation. II.The reaction profile has one transition state. III.The slow step is the first transition state. IV.The second step is attack of nuleophile on carbocation. V.The reaction proceeds in a polar aprotic solvent. A)I ,III ,and IV B)I ,II and IV C)II ,III and IV D)I ,II and V E)II,IV and V

Accepted Answer

Statement I suggests that the rate determining step involves the formation of a carbocation. This means that the slowest step in the reaction involves the breaking of a bond to form a carbocation. Statement II says that there is only one transition state in the reaction profile. This means that there is only one peak in the energy diagram that corresponds to a transition state. Statement III claims that the first transition state is the slow step in the reaction. This is in agreement with Statement I, because the formation of the carbocation involves the breaking of a bond and the loss of a leaving group, which is typically a slow step in organic reactions. Statement IV correctly states that the second step involves attack by a nucleophile on the carbocation. Statement V suggests that the reaction proceeds in a polar aprotic solvent, which is typically the best solvent for SN1 reactions.

Therefore, statements I, III, and IV are true and the correct answer is A.

Question 12

Organic reactions in which atoms or groups that are bonded to adjacent carbon atoms are eliminated are called elimination reactions.

Accepted Answer

This is a correct definition of elimination reactions in organic chemistry.

Question 13

Molecules add across multiple bonds in another molecule in addition reactions.

Accepted Answer

Addition reaction occurs when two or more molecules combine to form a single molecule. In this type of reaction, atoms or groups of atoms add to double or triple bonds in another molecule. Therefore, molecules do add across multiple bonds in addition reactions.

Question 14

Arrange the following carbocations in order of decreasing stability: 
A)A > B > C
B)C > B > A
C)B > C > A
D)C > A > B
E)B > A > C

Accepted Answer

The stability of carbocations is evaluated based on the number of electron-donating alkyl groups attached to the positively charged carbon. Therefore, the decreasing order of stability is A > B > C. In option D, carbocation C is the least stable because it has no alkyl groups attached to the positively charged carbon, while carbocation A is the most stable as it has three alkyl groups attached to it. Hence, option D is the correct choice.

Question 15

Arrange the following in the order of decreasing nucleophilicity: H₂N^-,HO^-,HCOO^-,CH₃O^- A)H₂N^-> HO^- > HCOO^- > CH₃O^- B)H₂N^-> CH₃O^-> HO^- > HCOO^- C)H₂N^-> HO^- > CH₃O^-> HCOO^- D)HO^- > H₂N^-> CH₃O^-> HCOO^- E)CH₃O^-> HO^- > H₂N^-> HCOO^-

Accepted Answer

Nucleophilicity increases with the increase in electron density and availability of the lone pair of electrons. Among the given options, CH₃O^- has the highest nucleophilicity as it has a higher electron density due to the sulfur atom and oxygen atom. H₂N^- has the next highest nucleophilicity due to the presence of two sulfur atoms. HO^- has a lower nucleophilicity due to the presence of an oxygen atom with only one lone pair of electrons. HCOO^- has the lowest nucleophilicity as the carbonyl group decreases the electron density on the oxygen atom, making it less nucleophilic. Hence, the correct order of decreasing nucleophilicity is CH₃O^- > H₂N^- > HO^- > HCOO^-. Statement B is the correct choice.

Question 16

For which type of reaction is the following an example? 
A)substitution
B)elimination
C)polymerization
D)rearrangement
E)addition

Accepted Answer

The answer of For which type of reaction is the...

Question 17

Reactions between alkanes and HX compounds are typical examples of addition reactions.

Accepted Answer

Reactions between alkanes and HX compounds are examples of substitution reactions, not addition reactions, because in these reactions, a hydrogen atom in the alkane is replaced (substituted) by a halogen atom from the HX compound.

Question 18

Finish the sentence:
"Elimination reactions...
A)...can follow two different mechanisms."
B)...do not compete with other reaction types."
C)...usually give a saturated product."
D)...always give only one product."
E)...have only one mechanistic path."

Accepted Answer

Elimination reactions can follow either the E1 or E2 mechanism, meaning there are two possible mechanistic paths for this type of reaction.

Question 19

We can promote S_N2 over S_N1 reactions if we: I.use a substrate that gives a primary carbocation and not tertiary carbocation II.use a sterically hindered substrate III.use a polar protic solvent A)I. B)II. C)III. D)I and III. E)II and III.

Accepted Answer

Using a substrate that gives a primary carbocation favors S_N2 reactions because primary carbocations are less stable and do not favor S_N1 reactions, which involve carbocation intermediates.

Question 20

In a substitution reaction an atom,an ion or a group in one molecule is replaced by another atom,ion or group.

Accepted Answer

This is exactly what happens in a substitution reaction - one atom, ion, or group is substituted with another in a molecule.

Quiz 27: Reactions of Organic Compounds

Synthesis of alkanes from alkyl halides is a typical example of E2 reaction.

Electrophilic substitution reactions are typical reactions of aromatic compounds.

Find the combination of conditions that are the best for SN2 reactions.

The step reaction polymerizations are fast polymerization reactions.

The alkanes are known for their reactivity.

Which of the following steps can be found in E1 reaction mechanism? I.formation of a carbocation II.attack of the base and removal of a proton from carbocation III.attack of a nucleophile IV.formation of a carboanion

Nucleophiles are electron poor atoms,ions or groups.

SN2 reactions are nucleophilic substitution reactions for which the rate determining step is bimolecular.

Organic reactions in which atoms or groups that are bonded to adjacent carbon atoms are eliminated are called elimination reactions.

Molecules add across multiple bonds in another molecule in addition reactions.

Arrange the following carbocations in order of decreasing stability:

Arrange the following in the order of decreasing nucleophilicity: H2N-,HO-,HCOO-,CH3O-

For which type of reaction is the following an example?

Reactions between alkanes and HX compounds are typical examples of addition reactions.

Finish the sentence: "Elimination reactions...

We can promote SN2 over SN1 reactions if we: I.use a substrate that gives a primary carbocation and not tertiary carbocation II.use a sterically hindered substrate III.use a polar protic solvent

In a substitution reaction an atom,an ion or a group in one molecule is replaced by another atom,ion or group.

Find the combination of conditions that are the best for S_N2 reactions.

S_N2 reactions are nucleophilic substitution reactions for which the rate determining step is bimolecular.

Arrange the following in the order of decreasing nucleophilicity: H₂N^-,HO^-,HCOO^-,CH₃O^-

We can promote S_N2 over S_N1 reactions if we: I.use a substrate that gives a primary carbocation and not tertiary carbocation II.use a sterically hindered substrate III.use a polar protic solvent