Question

Draw the structure for each alcohol. \begin{equation}\begin{array}{l}{\text { a. } 2 \text { -butanol }} \\ {\text { b. } 2 \text { -methyl-1-propanol }} \\ {\text { c. } 3 \text { -ethyl-1-hexanol }} \\ {\text { d. } 2 \text { -methyl-3-pentanol }}\end{array}\end{equation}

Short answer

2-butanol: CH3-CH(OH)-CH2-CH3. 2-methyl-1-propanol: CH3-CH(OH)-CH(CH3)2. 3-ethyl-1-hexanol: CH3-CH2-CH(CH2-CH3)-CH2-CH2-CH2OH. 2-methyl-3-pentanol: CH3-CH(OH)-CH2-CH(CH3)-CH3.

Step-by-step solution

Draw 2-butanol

First, draw a chain of four carbon atoms to represent butanol. The number '2' indicates that the OH group (hydroxyl group) is attached to the second carbon atom. The rest of the carbon atoms are filled with hydrogen atoms to satisfy the four bonds of each carbon.

Draw 2-methyl-1-propanol

Start with a chain of three carbon atoms for propanol. The '1' indicates the OH group is on the first carbon. The '2-methyl' indicates there is a CH3 (methyl) group attached to the second carbon. Complete the structure by adding hydrogen atoms to satisfy the four bonds of each carbon.

Draw 3-ethyl-1-hexanol

Draw a chain of six carbon atoms for hexanol. The '1' denotes the attachment of the OH group to the first carbon atom. The '3-ethyl' indicates an ethyl group (a two-carbon chain, CH2-CH3) is attached to the third carbon of the main chain. Add hydrogen atoms to complete the structure.

Draw 2-methyl-3-pentanol

Construct a chain of five carbon atoms for pentanol. The OH group is on the third carbon atom, due to the '3' in the name. A methyl group is on the second carbon atom, as indicated by '2-methyl'. Fill in all remaining valencies with hydrogen atoms.

Key concepts

Organic Compound Nomenclature

Understanding the nomenclature of organic compounds is essential in organic chemistry. It is like learning the alphabet before trying to spell words and sentences. The nomenclature for naming alcohols, a common class of organic compounds, follows the International Union of Pure and Applied Chemistry (IUPAC) guidelines. These guidelines help chemists to convey the structure of a molecule unambiguously. An alcohol's name typically ends in '-ol,' indicating the presence of a hydroxyl group.

• The root name tells the number of carbons in the longest continuous chain (e.g., 'pent' for five carbons).
• Numbering the carbon chain gives the position of the hydroxyl group as well as any other substituents (e.g., '2-butanol' has the OH on the second carbon).
• Additional groups attached to the main chain are referred to as substituents, and their position is also indicated by numbers (e.g., '2-methyl' in 2-methyl-1-propanol).

The process of naming an organic compound requires identifying these elements and assembling them in accordance with IUPAC rules for proper structure communication.

Drawing Chemical Structures

Drawing chemical structures is a practical skill for visualizing and understanding the composition of molecules. To draw an accurate chemical structure, you need to follow a set of systematic steps.
Start with identifying the backbone of the molecule, which usually consists of carbon atoms. Number the carbon chain if necessary, to show where functional groups or substituents are attached. Then, add these functional groups in their correct positions as indicated by the nomenclature.

• Draw single bonds as lines between atoms; however, double or triple bonds may also be represented if the molecule requires.
• Ensure that carbon atoms have four bonds (including to hydrogen atoms) and that oxygen in hydroxyl groups has two.

In drawings, hydrogen atoms are sometimes omitted for clarity, especially in larger structures, and are assumed to be attached to complete carbon's four bonds.

Functional Groups in Organic Chemistry

In organic chemistry, functional groups are specific groupings of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules. They are like distinct 'functional' areas within a complex factory.

• The hydroxyl group (-OH) defines alcohols and is responsible for their polar nature.
• Amino groups, carbonyl groups, and carboxyl groups are examples of other common functional groups, each providing different properties and reactivity.

By recognizing functional groups, chemists can predict how a molecule will behave in chemical reactions and understand the molecule's physical properties, such as solubility and boiling point.

Hydroxyl Group

The hydroxyl group, comprised of one oxygen atom bonded to one hydrogen atom (-OH), is a fundamental functional group in alcohols. Its presence defines the alcohol class of organic compounds. The hydroxyl group is highly polar, making alcohols generally more soluble in water than related hydrocarbons.
In nomenclature, the position of the hydroxyl group is crucial as it influences the compound's name. For instance, '1-propanol' and '2-propanol' are structurally different due to the position of the hydroxyl group along the carbon chain, despite both having three carbon atoms and a single hydroxyl group.