Reactions involving cleavage of the C-O bond include reaction with hydrogen halides and phosphorus halides, or dehydration. The Lucas test is an example of a C-O bond cleavage reaction.

Industrial preparation of ethanol often occurs via the fermentation of sugars.

The Lucas test uses concentrated $text{HCl}$ and anhydrous $text{ZnCl}_2$ (Lucas reagent) to distinguish between 1°, 2°, and 3° alcohols based on reactivity.

The -OH group is ortho and para directing in electrophilic aromatic substitution reactions.

Ethers are classified as simple (symmetrical) or mixed (unsymmetrical) depending on whether the alkyl/aryl groups attached to the oxygen atom are the same or different.

Dihydric phenols include catechol (Benzene-1,2-diol), resorcinol, and quinol.

Electron-withdrawing substituents, like $text{NO}_2$, increase the acidity of phenols by stabilizing the phenoxide ion.

Alcohols are generally weaker acids than water.

The neutral $text{FeCl}_3$ test yields a characteristic color (violet/purple) with phenols but not with alcohols, allowing for distinction.

Although not explicitly listed in the main reactions, phenol can be reduced to benzene using zinc dust. (If phenol undergoes reduction, it forms cyclohexanol, mentioned in. However, zinc dust leads to benzene, an established concept relating to the ring).

Ethers have lower boiling points because they cannot form intermolecular hydrogen bonds, unlike alcohols.

Phenol is prepared industrially from cumene (isopropylbenzene).

In alcohols, the carbon atom bonded to the -OH functional group is $sp^3$ hybridized.

The most common and versatile method for preparing ethers is the Williamson synthesis.

Strong oxidizing agents yield carboxylic acids, but milder or specific reagents are needed to stop at the aldehyde stage. ($text{CrO}_3$ is often used to stop oxidation at the aldehyde stage).

Ethers are named as alkoxyalkanes in the IUPAC system.

Alcohols containing only one hydroxyl (-OH) group are classified as monohydric alcohols.

Tertiary alcohols resist oxidation because the carbon atom bearing the -OH group does not have a hydrogen atom attached directly to it.

Alcohols exhibit significantly higher boiling points due to the presence of the -OH group, allowing them to form strong intermolecular hydrogen bonds.

This reaction, resulting in the introduction of an aldehyde group, is the Reimer-Tiemann reaction.

Methanol ($text{CH}_3text{OH}$) is commonly known as wood spirit.

The alkoxy group (-OR) is strongly activating and directs electrophiles to the ortho and para positions.

Reaction of Grignard reagents with formaldehyde yields primary alcohols. Using other aldehydes produces secondary alcohols, and ketones yield tertiary alcohols.

Alcohols can be prepared from alkyl halides via a substitution reaction, where the halogen is replaced by a hydroxyl group.

Ethers undergo C-O bond cleavage upon reaction with HI or HBr, forming alkyl halides. Diethyl ether forms ethyl iodide ($text{CH}_3text{CH}_2text{I}$).

Phenols undergo oxidation to form quinones.

Denatured alcohol is ethanol made unfit for drinking to prevent consumption and exempt it from heavy excise duties.

The formation of a tri-substituted product shows that the -OH group strongly activates the ring towards electrophilic substitution (Halogenation of phenol).

The phenoxide ion, the conjugate base of phenol, is stabilized by resonance, making phenol more acidic than alcohols.

Dehydration of alcohols yields ethers at lower temperatures (around 413 K or 140°C), favoring intermolecular dehydration. Higher temperatures (443 K) favor alkene formation.