Study Notes on Carboxylic Acids, Amines, and Amides

Organic compounds are categorized into families based on distinct functional groups.
A functional group is defined as an atom, group of atoms, or bond that imparts specific physical and chemical properties to a compound.

Carboxylic acids contain a carboxyl functional group (-COOH) attached to a hydrocarbon (alkyl group) part.
The carboxyl group consists of:
- A carbonyl group (C=O)
- A hydroxyl group (-OH)
The general depiction of the carboxyl group includes its notation as “COOH” or “CO2H.”

Chemists typically represent the general structure of a carboxylic acid using the letter “R” to denote an alkyl group or any organic group.

Acetic acid: Condensed structural formula is shown.
- White vinegar composition: 95% water and 5% acetic acid.
- Hydrocarbon part (R): Methyl group (CH₃).
- Ball-and-stick model description:
- Black sphere = carbon
- Red sphere = oxygen
- White sphere = hydrogen

Find and Name the Parent Chain:
- Longest continuous carbon chain containing the carbonyl carbon.
- Count all carbon atoms, including the carbonyl carbon.
- Replace the suffix “-e” of the respective alkane with “-oic acid.”
- Example:
  - Parent chain with three carbons is propanoic acid (from propane).
Name Any Alkyl Group Substituents:
- Use the same methodology as hydrocarbons for naming.
Determine Alkyl Group Attachment Point:
- Assign position numbers to the parent carbons starting from the carbonyl carbon.
- Assign numbers to substituents accordingly.
Construct the Final Name:
- Place alkyl group names in alphabetical order with position numbers.
- Include prefixes (di, tri, tetra) for identical substituents if applicable.
- Example: 3-methylbutanoic acid (with a methyl substituent).

Water solubility is influenced by the ability of the compound to interact with water.
Carboxylic acids attract water through hydrogen bonding and dipole-dipole interactions.
Small carboxylic acids show significant water solubility that decreases as the nonpolar hydrocarbon region increases.

Carboxylic acids are acids as they can donate H in reactions.
The reaction transfers a proton from the -OH group of the carboxylic acid to water, forming a carboxylate ion (A form that carries a -1 charge).
- Carboxylate ion = Acid form (carboxylic acid) + Base form (carboxylate anion)
Example: Ethanoic acid in water:
- Carboxylate ion is formed by changing “-ic acid” to “-ate ion”:
- Ethanoic acid → Ethanoate ion.

Used for predicting relative amounts of acid and base forms in solution based on the pH.
Example: Butanoic acid with pKa ~ 4.8 shows that a physiological pH (~7.4) would lead to a prevalence of the base form (butanoate ion).

Carboxylic acids react with hydroxide compounds (OH−) in a neutralization reaction producing water and carboxylic acid salts.
Examples:
- Propanoic acid + NaOH forming sodium propanoate (water soluble if R has <12 C).
- Salts of carboxylate ions are more water soluble than carboxylic acids.

An ester results when a carboxylic acid reacts with an alcohol, producing water in the process.
- General Reaction:
  ext{Carboxylic Acid} + ext{Alcohol}
  ightarrow ext{Ester} + ext{Water}
- Notation: R (carboxylic acid) and R' (alcohol).

Reverse of the amide reaction to produce a carboxylic acid and an amine (or ammonia).
- Hydrolysis occurs with heat and acid catalyst.

Removing a carboxyl group (COOH) and substituting a hydrogen atom.
Important in biological processes like the citric acid cycle.
- General Decarboxylation:
  ext{Carboxylic Acid}

Amines feature a nitrogen atom with a lone pair and single bonds to R (hydrocarbon groups) or hydrogen.
Classifications of amines:
- Primary (1º): one R group.
- Secondary (2º): two R groups.
- Tertiary (3º): three R groups.

Find the longest carbon chain associated with the nitrogen to determine the parent chain and apply similar rules as with alkanes.
For amines with more than two carbons, position numbers to show attachment to nitrogen must be assigned.

Contain a carbonyl group (C=O) attached to a nitrogen atom that’s bonded to the carbonyl carbon.
Example: Ethanamide with structural representations provided.

Find and Name Parent Chain: Same approach as carboxylic acids, converting -e to -amide.
- Example: Propanoic acid becomes propanamide.
Name Alkyl Group Substituents: Similar procedure by indicating positions and using N- for nitrogen attachments.
Construct Amide Name by listing any substituents alphabetically with the parent name.
- For example: N-methylpropanamide.

Formed via the reaction of carboxylic acids with ammonia or primary/secondary amines.
Illustrative reactions shown for clarity of the process.

Defined as cyclic compounds containing atoms other than carbon (e.g., nitrogen, oxygen).
Common examples include pyridine and purine.

Heterocycles play critical roles in biological systems, and notable examples are nicotine and adenosine triphosphate (ATP), essential for energy transfer in biological molecules.

Smaller amines possess strong odors and physiological roles include toxicity or biological activity.
Physiologically active amines are referred to as alkaloids.
- Examples: Morphine, heroin, etc.