Question

Directions: Each question contains Statement- 1 and Statement-2 and has the following choices (a), (b), (c) and (d), out of which ONLY ONE is correct. (a) Statement- 1 is True, Statement- 2 is True; Statement- 2 is a correct explanation for Statement-1 (b) Statement- 1 is True, Statement- 2 is True; Statement- 2 is NOT a correct explanation for Statement-1 (c) Statement- 1 is True, Statement- 2 is False (d) Statement- 1 is False, Statement- 2 is True Statement 1 Nucleophilicity does not always match with basicity. and Statement 2 While nucleophilicity is more related to size, polarizability and steric factors, the basicity is the ability to abstract a proton from a substrate.

Short answer

Explain your answer based on the provided statements. Answer: No, nucleophilicity and basicity do not always match up. While both involve interactions with other molecules, nucleophilicity is related to the ability to donate electrons for forming a chemical bond and is influenced by size, polarizability, and steric factors, whereas basicity is defined as the ability to accept a proton (H+ ion) from a substrate. Despite some similarities, they are influenced by different factors and thus do not necessarily match up.

Step-by-step solution

Statement-1: Nucleophilicity does not always match with basicity.

This statement is true. Nucleophilicity refers to the ability of an atom or molecule to donate a pair of electrons to another molecule to form a chemical bond. Basicity, on the other hand, refers to the ability of a molecule to accept a proton (H+, a hydrogen ion). While they may exhibit similar trends, nucleophilicity and basicity do not necessarily match up.

Statement-2: While nucleophilicity is more related to size, polarizability and steric factors, the basicity is the ability to abstract a proton from a substrate.

This statement is also true. The factors affecting nucleophilicity include size, polarizability, and steric hindrance. Larger, more polarizable, and less sterically hindered molecules tend to be better nucleophiles. Basicity is related to the ability of a molecule to accept a proton; it is related to different factors than nucleophilicity. Now, we can determine whether Statement-2 is a correct explanation for Statement-1.

Explanation Relationship

Statement-1 is true and Statement-2 is true; however, Statement-2 does not directly explain why nucleophilicity and basicity do not always match up. They both describe the characteristics of nucleophilicity and basicity separately, but Statement-2 does not provide a strong correlation or explanation for the difference. Based on our analysis, the correct answer choice is: (b) Statement-1 is True, Statement-2 is True; Statement-2 is NOT a correct explanation for Statement-1

Key concepts

Chemical Bond Formation

Chemical bond formation is a significant concept in chemistry, underpinning the interactions and reactivity of atoms and molecules. When nucleophiles donate a pair of electrons to electrophiles, they can create covalent bonds. This process allows the atoms or molecules to achieve a more stable electronic configuration.
The ability of a molecule to participate in chemical bond formation is affected by its nucleophilicity. Nucleophiles are typically electron-rich species, seeking to interact with electron-deficient molecules or sites. As such, their effectiveness in forming a chemical bond depends on factors like molecular structure and electronic configuration.

• Nucleophilicity: This involves the willingness and ability of an atom or molecule to donate electrons to form bonds.
• Reactivity of Bonds: Influenced by how readily a nucleophile can approach and react with an electrophile.
• Stability of the New Bond: Depends on how well the nucleophile matches the needs of the electrophile.

Understanding chemical bond formation is essential for predicting how substances will react under various conditions.

Proton Abstraction

Proton abstraction is a core concept linked to the basicity of compounds. Basicity refers to the ability of a molecule to accept a proton ( \(H^+\), a hydrogen ion) from another molecule. This is an essential characteristic of bases, driving many chemical reactions that involve proton transfer.
In chemical processes, bases deprotonate acids by pulling away protons, altering the balance of the substances involved. The success of proton abstraction depends on several factors, such as the strength of the base and the acidity of the proton-donating molecule.

• Strength of the Base: Strong bases are more efficient at accepting protons.
• Acidity of the Proton Source: Easier proton abstraction from more acidic sources.
• Reaction Environment: Solvent and temperature can influence the process.

By understanding proton abstraction, you can predict how a base will interact in a given chemical setting.

Steric Hindrance

Steric hindrance refers to the physical obstruction caused by bulky groups within a molecule, affecting how reactions proceed. Large groups surrounding a reactive site can impede the access of nucleophiles or other reactants, slowing down or even preventing reactions.
In terms of nucleophilicity, steric hindrance plays a critical role. Smaller, less hindered nucleophiles are typically more effective because they can approach and react with electrophiles more easily than larger, bulky counterparts.

• Impact on Nucleophilicity: Less crowded or smaller molecules are better nucleophiles.
• Reaction Rates: Reactions are slower in highly hindered environments.
• Design in Chemical Reactions: Understanding steric effects helps in designing better synthetic routes.

Factoring in steric hindrance can significantly alter the expected outcome of a reaction.

Polarizability

Polarizability is a concept that reflects how easily the electron cloud around an atom or molecule can be distorted. It's key to understanding various chemical behaviors, including nucleophilicity.
The greater the polarizability, the more easily a molecule can engage in reactions, especially those involving electron donation. It is a critical consideration for nucleophiles, as more polarizable molecules are generally better at forming bonds.

• Influence on Nucleophilicity: Greater polarizability enhances nucleophilic behavior.
• Impact on Chemical Reactions: Highly polarizable species can be more reactive.
• Determination by Size and Electrons: Atoms with larger, more diffuse electron clouds are more polarizable.

Understanding polarizability can help predict how an atom or molecule will interact in various chemical scenarios.

Size Effect in Chemistry

The size effect in chemistry relates to how the size of an atom or molecule influences its chemical properties and reactivity. This plays an important role in differentiating nucleophilicity and basicity.
Larger atoms tend to be more polarizable and can form more stable interactions due to their extensive electron clouds. However, size can also introduce steric hindrance, influencing how readily a nucleophile can engage in reactions.

• Influence on Nucleophilicity: Larger size often means better nucleophilicity due to increased polarizability.
• Size vs. Steric Hindrance: Larger atoms can cause steric issues, impacting reactivity.
• Nucleophilicity vs. Basicity: While size boosts nucleophilicity, it doesn't necessarily increase basicity.

Recognizing the size effect helps to anticipate the reactivity and interaction potential of different chemical species.