University:
Whitman College
Course:
CHEM-245 | Organic Chemistry I
Academic year:

2023
Views:

278

Pages:

1
Author:

esfredint7qo

PHYSICAL PROPERTIES OF CARBOXYLIC ACID Physical Properties of Acids and Acid Derivatives (1) Boiling point Carboxylic acids have higher boiling points compared to alcohols, ketones, or aldehydes with similar molecular weights. 0 Cha-C-OH acetic acid, bd 118°C CHCH2CH2OH 1-propanol bd 97°C 0 CH3CH2CH Propionaldehyde bd 49°C The high boiling points of carboxylic acids is the result of formation of a stable hydrogen-bonded dimer. R-= O-HO hydrogen bonded acid dimer C-R (2) Melting points Melting points of carboxylic acids exhibit no consistent pattern. However, when considering carboxylic acids with up to 10 carbon atoms, those with an even number of carbon atoms tend to have higher melting points compared to neighboring members with an odd number of carbon atoms. This is due to the fact that carboxylic acid and methyl groups in even-numbered members are positioned on opposite sides of the zig-zag carbon chain, leading to a better fit within the crystal lattice, which results in higher melting points. Conversely, the opposite trend is observed in the case of carboxylic acids with an odd number of carbon atoms. COOH H3 Higher melting point MCOOH COOH Lower melting point Amides exhibit remarkably elevated boiling and melting points when compared to compounds of similar molecular weight. This phenomenon can be attributed to the strong hydrogen bonding that primary and secondary amides engage in. (3) Solubility Carboxylic acids have the ability to form hydrogen bonds with water, and carboxylic acids with lower molecular weights (up to 4 carbon atoms) are miscible with water. Acid derivatives, including esters, acid chlorides, anhydrides, nitriles, and amides, exhibit solubility in common organic solvents such as alcohols, ethers, chlorinated alkanes, and aromatic hydrocarbons. However, it's important to note that acid chlorides and anhydrides cannot be utilized in nucleophilic solvents like H2O and alcohols due to their reactivity with these solvents.

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