Aromatic Compounds 4

A substance that accepts a proton (H+).

A substance that donates an electron pair.

A measure of the basicity of a substance, inverse log of Kb

Measure of acidity of a substance's conjugate acid; related to pKb by the equation pKa + pKb = 14.

The substance formed when a base accepts a proton (H+).

Equilibrium constant for a base reacting with water.

Ammonia (NH3) forms a salt rather than water when reacting with an acid, even though it acts as a proton acceptor and electron pair donor.

Organic compounds similar to ammonia that act as bases.

Aspirin is a weak acid with a pKa of 3.5, meaning it's fully dissociated at physiological pH (7.4).

Morphine is a weak base with a pKa of 7.9, making it partially ionized at physiological pH (7.4).

Phenols are compounds with a hydroxyl group (-OH) directly attached to an aromatic ring.

Phenols are often named as derivatives of the simplest member, phenol, or as hydroxy-compounds.

Simple phenols are liquids or low-melting solids with high boiling points due to hydrogen bonding. They are soluble in water due to H-bonding.

Phenols are acidic, with a pKa around 10, because the aromatic ring stabilizes the negative charge of the phenoxide ion.

The key difference is the -OH group's position: directly attached to an aromatic ring in phenols, but to an aliphatic carbon in alcohols.

Phenols are easily oxidized, leading to colored compounds. They are also more reactive than alcohols due to the aromatic ring.

The strength of intermolecular hydrogen bonding between nitrophenol molecules determines its boiling point. Stronger hydrogen bonding leads to a higher boiling point.

Meta- and para-nitrophenols can form hydrogen bonds with water molecules due to the presence of the hydroxyl group (-OH) and the nitro group (-NO2). This interaction allows them to dissolve in water.

Ortho-nitrophenol exhibits intramolecular hydrogen bonding between its hydroxyl group (-OH) and the nitro group (-NO2) within the same molecule. This prevents the formation of intermolecular hydrogen bonds.

A hydrogen bond formed between atoms within the same molecule. This type of interaction is crucial in ortho-nitrophenol.

A hydrogen bond formed between atoms of different molecules. This interaction is important in meta- and para-nitrophenols.

Ortho-nitrophenol has the lowest boiling point due to intramolecular hydrogen bonding, followed by meta- and para-nitrophenols which have higher boiling points due to intermolecular hydrogen bonding.

Meta- and para-nitrophenols are more soluble in water than ortho-nitrophenol. This is because they can form hydrogen bonds with water molecules.

Ortho-nitrophenol's intramolecular bonding reduces the ability to form intermolecular hydrogen bonds with water molecules, leading to lower solubility.

o-Nitrophenol has a lower boiling point than its m- and p- isomers. This is due to intramolecular hydrogen bonding, which prevents strong intermolecular interactions.

o-Nitrophenol has poor water solubility compared to its m- and p- isomers. This is because the intramolecular hydrogen bonding reduces its ability to form hydrogen bonds with water.

The phenoxide ion is stabilized through resonance, which delocalizes the negative charge over the aromatic ring.

Phenols react with aqueous NaOH to form their salts (phenoxides).

Phenol salts react with carbonic acid (H2CO3) or other weak acids to regenerate the free phenols.

Salicylic acid, a precursor to aspirin, is acidic due to its phenolic group.

Salicylic acid is reacted with acetic anhydride to make aspirin, masking the phenolic group as an ester and preventing gastric bleeding.

A measure of the strength of a base; the higher the pKb value, the weaker the base.

The pKa of a conjugate acid and the pKb of its corresponding base are related by the equation pKa + pKb = 14.

Ammonia (NH3) and similar organic compounds (amines) act as bases by accepting protons, but form salts instead of water when reacting with acids.

Salicylic acid is a phenol that reacts with acetic anhydride to form aspirin, masking the phenolic group.

Meta- and para-nitrophenols have higher boiling points than ortho-nitrophenol due to stronger intermolecular hydrogen bonding.

Meta- and para-nitrophenols are more soluble in water than ortho-nitrophenol because they can form hydrogen bonds with water molecules.

Ortho-nitrophenol forms an intramolecular hydrogen bond, preventing it from forming hydrogen bonds with water molecules, making it less soluble.

Ortho-nitrophenol has a lower boiling point because the intramolecular hydrogen bond reduces intermolecular attractions.

Stronger intermolecular hydrogen bonding leads to higher boiling points.

Ortho-nitrophenol exhibits intramolecular hydrogen bonding between its hydroxyl (-OH) and nitro (-NO2) group within the same molecule, while meta and para nitrophenols form intermolecular hydrogen bonds.

Aspirin, a weak acid with a pKa of 3.5, is fully dissociated at physiological pH (7.4).

Morphine, a weak base with a pKa of 7.9, is partially ionized at physiological pH (7.4).

Hydrogen bonds form between the hydroxyl groups of different phenol molecules.

Hydrogen bonds occur within the same phenol molecule, usually between the -OH and a nearby electronegative group.

The strength of hydrogen bonding between nitrophenol molecules determines their boiling point. Ortho-nitrophenol has weaker intermolecular hydrogen bonding due to intramolecular hydrogen bonding, leading to a lower boiling point compared to meta- and para-nitrophenols.

Ortho-nitrophenol forms intramolecular hydrogen bonds within the molecule, which reduces its ability to form intermolecular hydrogen bonds with water molecules, leading to lower solubility.

Phenols are significantly more acidic than alcohols due to resonance stabilization in the phenoxide anion. The resonance delocalizes the negative charge, making the phenoxide ion more stable and increasing phenol's acidity.

The phenoxide anion is stabilized by resonance. This delocalization of the negative charge across the benzene ring makes the phenoxide ion more stable, contributing to the acidity of phenols.

Phenols react with aqueous NaOH to form their salts, called phenoxides. This reaction is driven by the formation of the more stable phenoxide ion.

Phenol salts react with carbonic acid (H2CO3) or other weak acids to regenerate the free phenols. This is a reversible reaction.

Salicylic acid, a precursor to aspirin, is a good analgesic due to its phenolic group. However, this group also causes gastric bleeding.

Aspirin is synthesized by reacting salicylic acid with acetic anhydride, masking the phenolic group as an ester. This prevents the gastric bleeding caused by the free phenolic group.