Lecture 6: Chemical Properties and Reactions of Alcohols

Vocabulary flashcards covering the chemical properties and reactions of alcohols, focusing on O-H bond rupture, acidity, esterification, and oxidation pathways.

Active centres

The polar or ionic bonds (C-O and O-H) and unshared pairs of electrons on the oxygen atom in alcohols that allow them to interact with polar or ionic reagents.

Acid ionization constant ($K_a$) of ethyl alcohol

A value of approximately $10^{-18}$, which indicates that alcohols are slightly weaker acids than water.

Acidity order of alcohols

The relative strength of acidity among the three types of alcohols, ranked as $1^\text{o} > 2^\text{o} > 3^\text{o}$.

+I effect (Inductive Effect)

The electron-releasing effect of alkyl groups toward the oxygen atom in alcohols, which increases negative charge on oxygen and makes the release of the proton ($H^+$) more difficult.

Metal alkoxides

Compounds formed when alcohols react with alkali metals (like Na or K), metal hydrides (MH), or metal amides ($MNH_2$), resulting in the liberation of hydrogen gas or other byproducts.

Williamson synthesis

A reaction used for the preparation of ethers where a sodium alkoxide ($R-ONa$) reacts with an alkyl halide ($R'-X$).

Esterification

A reversible reaction where alcohols react with carboxylic acids in the presence of an inorganic acid catalyst (like sulphuric acid) to form esters and water.

Oxidation (Organic Chemistry)

The removal of hydrogen from the carbon bearing the OH group and from the oxygen atom, resulting in the formation of a carbonyl group ($C=O$).

$⍺$ hydrogen (Alpha hydrogen)

The hydrogen atom attached to the carbon atom that is directly bonded to the hydroxyl ($-OH$) group; it is removed during the oxidation of alcohols.

Oxidation of primary ($1^\text{o}$) alcohols

A process that first produces an aldehyde and then a carboxylic acid, both containing the same number of carbon atoms as the parent alcohol.

Oxidation of secondary ($2^\text{o}$) alcohols

A process that yields a ketone with the same number of carbon atoms as the original alcohol; vigorous oxidation can further break the carbon skeleton into lower carboxylic acids.

Oxidation of tertiary ($3^\text{o}$) alcohols

Alcohols that are resistant to oxidation in alkaline solutions because they lack $⍺$ hydrogen atoms; however, drastic acidic oxidation yields a mixture of a ketone and a carboxylic acid with fewer carbon atoms.

Catalytic Dehydrogenation

The process of oxidizing alcohols by removing hydrogen atoms (as $H_2$) by passing alcohol vapors over a heated metal catalyst, such as reduced copper at $3000$, or silver.

Acetals

Compounds formed when alcohols combine with acetylene in the presence of mercury compounds as catalysts.