Question

The IUPAC name for a carboxylic acid is based on the name of the hydrocarbon with the same number of carbon atoms. The ending-oic is appended, as in ethanoic acid, which is the IUPAC name for acetic acid. Draw the structure of the following acids: (a) methanoic acid, (b) pentanoic acid, (c) 2-chloro-3-methyldecanoic acid.

Short answer

The structures of the given carboxylic acids are as follows: a) Methanoic acid - HCOOH b) Pentanoic acid - CH_3CH_2CH_2CH_2COOH c) 2-chloro-3-methyldecanoic acid - ClCH(CH_3)CH_2CH_2CH_2CH_2CH_2CH_2COOH

Step-by-step solution

Identify the number of carbon atoms from the IUPAC names

Look at the IUPAC name of the carboxylic acid and identify the number of carbon atoms in the molecule by finding the root word. For example, "meth-" means 1 carbon atom, "eth-" means 2 carbon atoms, "prop-" means 3 carbon atoms, etc. a) Methanoic acid - 1 carbon atom b) Pentanoic acid - 5 carbon atoms c) 2-chloro-3-methyldecanoic acid - 10 carbon atoms

Draw the basic carboxylic acid structure

A carboxylic acid is an organic compound containing a carboxyl group attached to an R group (which can be a hydrogen atom or an alkyl group). The general structure is R-COOH, where the carboxyl group consists of a carbon atom double-bonded to an oxygen atom and single-bonded to a hydroxyl group \((-OH)\). Draw the main chain of the carboxylic acid by attaching the appropriate number of carbon atoms from Step 1. a) Methanoic acid - HCOOH b) Pentanoic acid - CH_3CH_2CH_2CH_2COOH c) 2-chloro-3-methyldecanoic acid - (CH_3)_2CHCH_2CH_2CH_2CH_2CH_2COOH

Add substituents to the structure

Add substituents (functional groups or atoms replacing a hydrogen atom on the hydrocarbon chain) to the basic carboxylic acid structure as indicated by the IUPAC names. In this step, we'll be adding the substituents for 2-chloro-3-methyldecanoic acid. For 2-chloro-3-methyldecanoic acid, we have two substituents: - Chlorine atom (\(-Cl\)) at the 2nd carbon atom - Methyl group (\(-CH_3\)) at the 3rd carbon atom Now, add these substituents to the decanoic acid backbone from Step 2c: 2-chloro-3-methyldecanoic acid - ClCH(CH_3)CH_2CH_2CH_2CH_2CH_2CH_2COOH

Display the final structures

Now we have the structures for each of the given carboxylic acids: a) Methanoic acid - HCOOH b) Pentanoic acid - CH_3CH_2CH_2CH_2COOH c) 2-chloro-3-methyldecanoic acid - ClCH(CH_3)CH_2CH_2CH_2CH_2CH_2CH_2COOH

Key concepts

Carboxylic Acid Structure

Understanding the structure of carboxylic acids is foundational in organic chemistry. A carboxylic acid is characterized by a carboxyl group (-COOH), which consists of a carbon atom (C) double-bonded to an oxygen atom ( =O), and a hydroxyl group (-OH) attached to the same carbon atom. This functional group is key to identifying carboxylic acids and determines many of their reactive properties.

When illustrating a carboxylic acid's structure, like methanoic acid (HCOOH), the single carbon atom is shown bonded to an -OH group and a double-bonded oxygen. As we move to larger carboxylic acids, such as pentanoic acid (CH_3CH_2CH_2CH_2COOH), we start with the methyl group (CH_3) and extend the chain to include four more carbon atoms before ending with the carboxyl group.

Substituents can alter the structure and properties of carboxylic acids. In the example of 2-chloro-3-methyldecanoic acid, a chlorine (-Cl) and a methyl group (-CH_3) are attached at specified locations, altering the molecule's physical and chemical behavior. Hence, understanding the structure not only aids in drawing these compounds correctly but also in predicting their reactivity and properties.

Organic Chemistry Nomenclature

The nomenclature in organic chemistry is standardized to avoid confusion when identifying and communicating about organic compounds. The system used is created by the International Union of Pure and Applied Chemistry (IUPAC), which provides rules and guidelines for naming organic compounds systematically. In the context of carboxylic acids, the IUPAC nomenclature is centered around the longest carbon chain to which the carboxyl group is attached and includes indications of any other functional groups present.

To name a carboxylic acid following IUPAC rules, one must identify the longest carbon chain, use an appropriate prefix (like meth- for one carbon, pent- for five, etc.), and attach the suffix -oic acid. For example, pentanoic acid refers to a chain of five carbon atoms ending in a carboxyl group. If substituents are present, their position and nature are indicated by numbers and names, respectively, as is seen in 2-chloro-3-methyldecanoic acid. This systematic approach ensures clear communication in the scientific community.

Functional Groups in Organic Compounds

Functional groups are specific groupings of atoms within molecules that are responsible for the characteristic chemical reactions of those compounds. They play a crucial role in organic chemistry as they define the reactivity and properties of molecules. Carboxylic acids contain one of the most common functional groups, the carboxyl group (-COOH), but they can also have others, such as hydroxyl groups (-OH), halogens like chlorine (-Cl), or alkyl groups (-CH_3), among others.

For instance, in 2-chloro-3-methyldecanoic acid, besides the carboxyl group, there are two more functional groups: a chlorine atom and a methyl group. These substituents are named and numbered based on where they are attached to the main carbon chain. The presence of these groups not only influences the molecule's name but also its behavior in chemical reactions. Understanding functional groups helps predict a molecule's physical properties, such as solubility and boiling point, and its reactivity in chemical processes.