Problem 50 - Chemistry: The Central Science in SI Units, Global Edition

Question

Draw the condensed structures of the compounds formed from (a) butanoic acid and methanol, (b) benzoic acid and 2 -propanol, \((\mathbf{c})\) propanoic acid and dimethylamine. Name the compound in each case.

Step-by-Step Solution

Answer

(a) The condensed structure of the ester formed by butanoic acid and methanol is CH3CH2CH2COOCH3, and the IUPAC name is Methyl butanoate. (b) The condensed structure of the ester formed by benzoic acid and 2-propanol is C6H5COOCH(CH3)2, and the IUPAC name is Isopropyl benzoate. (c) The condensed structure of the amide formed by propanoic acid and dimethylamine is CH3CH2CON(CH3)2, and the IUPAC name is N,N-Dimethylpropanamide.

Step 1: (a) Butanoic acid and Methanol

To create the compound from butanoic acid and methanol, we will perform an esterification reaction. In this reaction, the carboxylic acid (butanoic acid) reacts with the alcohol (methanol) to form an ester and water. The reaction is as follows: Butanoic Acid + Methanol → Ester + Water The ester group (-O- group) will connect the butanoic acid and methanol. The condensed structure of the ester formed by this reaction is: CH3CH2CH2COOCH3 The IUPAC name of this compound is "Methyl butanoate" since the butanoic acid provides the "butanoate" part and the methanol provides the "methyl" part of the name.

Step 2: (b) Benzoic acid and 2-propanol

In this case, we will consider an esterification reaction between benzoic acid and 2-propanol. The reaction can be represented as: Benzoic Acid + 2-Propanol → Ester + Water The ester group (-O- group) will connect the benzoic acid and 2-propanol. The condensed structure of the ester formed by this reaction is: C6H5COOCH(CH3)2 The IUPAC name of this compound is "Isopropyl benzoate" since the benzoic acid provides the "benzoate" part and the 2-propanol provides the "isopropyl" part of the name.

Step 3: (c) Propanoic acid and dimethylamine

For this case, we will perform a reaction between the carboxylic acid (propanoic acid) and an amine (dimethylamine) to form an amide. The reaction can be represented as: Propanoic Acid + Dimethylamine → Amide + Water The amide group (-CONH- group) will connect the propanoic acid and dimethylamine. The condensed structure of the amide formed by this reaction is: CH3CH2CON(CH3)2 The IUPAC name of this compound is "N,N-Dimethylpropanamide" since the propanoic acid provides the "propanamide" part and the dimethylamine provides the two "methyl" groups bonded to the nitrogen atom.

Key Concepts

Carboxylic Acid

In the world of organic chemistry, carboxylic acids are a fundamental family of compounds. Recognizable by their functional group, \(-COOH\), these acids have a carbon atom double-bonded to an oxygen atom and single-bonded to a hydroxyl group. This grouping makes them both a bit acidic and reactive, which is key for syntheses like esterification.

Carboxylic acids derive their name from their acidic properties, releasing hydrogen ions (H⁺) in solutions, similar to inorganic acids. However, their reactivity isn't solely limited to their acidic nature. Carboxylic acids are often transformed through reactions to form various derivative compounds. One common transformation is esterification, where the carboxylic acid reacts with an alcohol to form an ester, releasing water as a byproduct.

• The reaction is reversible, which means conditions like temperature and the presence of catalysts can affect the yield of esters.
• In practical applications, this process is valuable for creating flavors and fragrances.

For instance, in the original exercise, butanoic acid and propanoic acid are examples of carboxylic acids participating in such reactions.Their names signify the number of carbon atoms they contain, making them a focus in structural and functional diversity of organic chemistry.

IUPAC Nomenclature

The International Union of Pure and Applied Chemistry (IUPAC) has established a consistent method for naming chemical compounds, known as IUPAC nomenclature. This allows chemists worldwide to communicate structures and reactions clearly. Understanding this system can be likened to learning a new language of chemistry.

For individuals tackling chemical nomenclature, each name provides significant data about the compound's structure:

• "Butanoate" in "Methyl butanoate" comes from butanoic acid, consistent with adding the -oate suffix to carboxylic acid names.
• "Methyl", "Isopropyl", and "Dimethyl" describe the alcohol or amine part of the ester/amide.

Consider how each segment of an IUPAC name gives clues about the functional groups and carbon chains involved:
"Isopropyl benzoate" stands as another example:

• "Benzoate" indicates the presence of a benzoic acid-derived ester.
• "Isopropyl" specifies the alcohol portion coming from 2-propanol.

Comprehending these naming conventions not only facilitates understanding between chemists but also provides insight into the molecular structure without seeing a chemical drawing.

Amide Formation

Amides are versatile and significant compounds in chemistry, formed typically from the reaction of a carboxylic acid and an amine. In this reaction, the -OH group from the acid and a hydrogen from the amine combine to form water, leaving the -CON- linkage intact.

The process of forming an amide from a carboxylic acid and an amine is straightforward, but significant in forming polymeric materials like nylon and proteins:

• Carboxylic acid contributes the \(-COOH\) group while the amine provides \(-NH_2\), leading to our functionality: \(-CONH-\).
• Amides, due to their strong carbon-nitrogen bonds, have unique stability and properties.

In the original exercise, propanoic acid reacting with dimethylamine forms "N,N-Dimethylpropanamide". This name reflects both the amide bond ("propanamide") and the presence of the two methyl groups on the nitrogen ("N,N-Dimethyl").
Understanding amide formation opens doors to grasping polymer science, where the strength of the amide bond is crucial in the stability of synthetic and natural materials.