chapter 4: analyzing organic reactions

What do secondary alcohols oxidize to?

Ketones by most oxidizing agents.

What do aldehydes oxidize to?

Carboxylic acids by most oxidizing agents.

What is reduction in terms of oxidation state?

A decrease in oxidation state, assisted by reducing agents.

What characterizes reducing agents?

Donate electrons, Have low electronegativity and ionization energy, Often contain a metal and hydrides.

What functional groups are targeted in chemoselectivity?

Highest-priority (most oxidized) functional groups.

How can one utilize steric hindrance?

To selectively target or protect functional groups in a reaction.

What are diols used for?

As protecting groups for aldehyde or ketone carbonyls.

How are alcohols protected?

By conversion to tert-butyl ethers.

What are the two steps involved in SN1 reactions?

Leaving group departs, forming a carbocation; Nucleophile attacks the planar carbocation, resulting in a racemic mixture.

Why do SN1 reactions prefer more substituted carbons?

Alkyl groups donate electron density, stabilizing the positive charge of the carbocation.

What is the rate expression for an SN1 reaction?

rate = (k[R-L])

Describe the process of SN2 reactions.

Nucleophile attacks while leaving group departs; Backside attack leads to inversion of stereochemistry.

What happens to absolute configuration during SN2 reactions?

Changes from (R) to (S) or vice versa if the nucleophile and leaving group have the same priority.

Why do SN2 reactions prefer less-substituted carbons?

More substituents create steric hindrance, inhibiting nucleophile access.

What is the rate expression for an SN2 reaction?

rate = (k[Nu:][R-L])

What defines the oxidation state of an atom?

The charge it would have if all bonds were completely ionic.

Which compound has the lowest oxidation state of carbon?

CH₄ (most reduced)

What is the highest oxidation state of carbon?

CO₂ (most oxidized)

List the order of oxidation in functional groups from most oxidized to least.

Carboxylic acids, Aldehydes, Ketones, Imines, Alcohols, Alkyl halides, Amines

What is oxidation in terms of oxidation state?

An increase in oxidation state, facilitated by oxidizing agents.

What role do oxidizing agents play?

They accept electrons and are reduced, often having a high affinity for electrons.

Which functional groups are considered the most oxidized?

Carboxylic acids and carboxylic acid derivatives.

What are Lewis acids?

Lewis acids are electron acceptors; they have vacant orbitals or positively polarized atoms.

What defines a Lewis base?

Lewis bases are electron donors; they have a lone pair of electrons and are often anions.

Define Brønsted-Lowry acids.

Brønsted-Lowry acids are proton donors.

What is a Brønsted-Lowry base?

Brønsted-Lowry bases are proton acceptors.

What are amphoteric molecules?

Amphoteric molecules can act as either acids or bases, depending on reaction conditions.

What is the acid dissociation constant (Kₐ)?

Kₐ measures acidity, representing the dissociation of an acid into a proton and its conjugate base.

What does pKa represent?

pKa is the negative logarithm of Kₐ; a lower pKa indicates a stronger acid.

How does pKa change in the periodic table?

pKa decreases down the periodic table and as electronegativity increases.

what are the common acidic functional groups?

Alcohols, Aldehydes, Ketones, Carboxylic acids, Carboxylic acid derivatives

What are α-hydrogens?

α-hydrogens are hydrogens connected to an α-carbon, a carbon adjacent to a carbonyl, and are acidic.

what are the basic functional groups?

Amines and Amides

What are nucleophiles?

Nucleophiles are 'nucleus-loving' species that contain lone pairs or π bonds and have increased electron density.

How does nucleophilicity relate to basicity?

Nucleophilicity is similar to basicity; however, it is a kinetic property versus basicity which is thermodynamic.

What factors affect nucleophilicity?

Charge, electronegativity, steric hindrance, and the solvent can all affect nucleophilicity.

Give an example of a common organic nucleophile.

Amino groups are common organic nucleophiles.

Define electrophiles.

Electrophiles are 'electron-loving' species that contain a positive charge or are positively polarized.

What makes a compound more electrophilic?

More positive compounds are more electrophilic.

List substances that can act as electrophiles.

Alcohols, Aldehydes, Ketones, Carboxylic acids, Derivatives

What are leaving groups?

Leaving groups are molecular fragments that retain electrons after heterolysis.

What characterizes the best leaving groups?

The best leaving groups can stabilize additional charge through resonance or induction.

What type of bases make good leaving groups?

Weak bases (the conjugate bases of strong acids) make good leaving groups.

Are alkanes and hydrogen ions good leaving groups?

Alkanes and hydrogen ions are almost never leaving groups because they form reactive anions.

what does LiAlH4 reduce aldehydes to

alcohols

what does LiAlH4 reduce ketones to

alcohols

what does LiAlH4 reduce carboxylic acids to

alcohols

what does LiAlH4 reduce amides to

amines

what does LiAlH4 reduce esters to

a pair of alcohols