BackAlcohols and Phenols - General Chemistry
01:10
Terms in this set (30)
An alcohol is a compound where a hydroxyl group (-OH) is attached to a saturated carbon atom (sp3 hybridized).
Enols have a hydroxyl group attached to an unsaturated carbon (sp2), while phenols have the hydroxyl group directly attached to a benzene ring.
Alcohols are classified as primary, secondary, or tertiary depending on whether the carbon bonded to -OH is attached to one, two, or three other carbons.
The general formula is \(\mathrm{C_nH_{2n+1}OH}\) or R-OH.
Select the longest carbon chain with the hydroxyl group, replace the alkane suffix 'e' with 'ol', and number the chain to give the hydroxyl carbon the lowest number.
Alcohols with two hydroxyl groups are called glycols or diols, and those with three hydroxyl groups are triols.
Because they can form hydrogen bonds due to the polar O-H group, increasing intermolecular forces.
Hydrogen bonding requires a lone pair on an electronegative atom and a polarized bond where hydrogen is bonded to N, O, or F.
Water molecules can form four hydrogen bonds due to two hydrogens and two lone pairs, while alcohols have fewer hydrogen bonds because one hydrogen is replaced by an alkyl group.
Ethylene glycol has two -OH groups, allowing more hydrogen bonding and a higher boiling point (197°C) than 1-propanol with one -OH (97°C).
o-Nitrophenol forms intramolecular hydrogen bonds, lowering boiling point (~214°C), while p-nitrophenol forms intermolecular hydrogen bonds, raising boiling point (~279°C).
Longer hydrocarbon chains decrease water solubility because the molecule becomes more hydrophobic.
More branching lowers boiling point but increases water solubility.
Phenols are stronger acids (Ka ~ 10^-10) than alcohols (Ka ~ 10^-16) due to resonance stabilization of the phenoxide ion.
Because the negative charge is delocalized over the aromatic ring by resonance, stabilizing the phenoxide ion.
Hydration of alkenes, hydrolysis of alkyl halides, and reduction of carbonyl compounds.
Reactions involving cleavage of the O-H bond (e.g., ionization, ester formation, oxidation) and cleavage of the C-O bond (e.g., dehydration, substitution).
Primary alcohols oxidize to aldehydes and carboxylic acids, secondary to ketones, and tertiary alcohols resist oxidation.
Phenols react to form water-soluble sodium phenoxide salts due to their acidity; alcohols generally do not react with aqueous NaOH.
Methanol (wood alcohol) is toxic because its metabolites (formaldehyde, formic acid) cause metabolic acidosis and optic nerve damage.
By administering ethanol, which competes for alcohol dehydrogenase, slowing methanol metabolism to toxic products.
Ethanol (grain alcohol) is produced by fermentation of sugars using yeast and is the alcohol in beverages.
Used as a disinfectant, solvent for drugs, and historically as an anesthetic and painkiller.
Used as rubbing alcohol and disinfectant; it is more toxic than ethanol.
Glycols are diols with hydroxyl groups on adjacent carbons; geminal diols have two hydroxyls on the same carbon and are usually unstable.
Glycerol is a triol, viscous and nontoxic, used as a moistening agent and a backbone in triglycerides and phospholipids.
Phenols are aromatic compounds with hydroxyl groups; they serve as disinfectants and are found in natural products like flavonoids and hormones.
Joseph Lister pioneered antiseptic surgery using phenol to sterilize instruments and wounds, reducing infections.
Flavonoids, tannins, lignin, and salicylic acid, which serve roles in defense, pigmentation, and signaling.
Estrogens (estradiol) and thyroid hormones (thyroxine, triiodothyronine) contain phenol rings essential for their biological activity.