Question

Draw a structural formula for each of the following alcohols. Indicate whether the alcohol is primary, secondary, or tertiary. a. 2 -propanol b. 2 -methyl- 2 -propanol c. 4 -isopropyl- 2 -heptanol d. 2,3 -dichloro- 1 -pentanol

Short answer

The structural formulas and types of the alcohols are: a. 2-propanol: CH₃-CH(OH)-CH₃, secondary alcohol b. 2-methyl-2-propanol: CH₃-C(OH)(CH₃)₂, tertiary alcohol c. 4-isopropyl-2-heptanol: CH₃CH(OH)CH₂CH(CH₃)₂CH₂CH₂CH₃, secondary alcohol d. 2,3-dichloro-1-pentanol: OH-CH(Cl)CH(Cl)CH₂CH₃, primary alcohol

Step-by-step solution

Draw the Skeleton of Propane

Start by drawing propane with three carbon atoms and draw all the hydrogen atoms surrounding the carbon atoms. The structure of propane will be: CH3-CH2-CH3

Replace One Hydrogen With the Hydroxyl (OH) Group

The alcohol is 2-propanol, therefore, replace the hydrogen in the middle carbon with the OH group. The structure of 2-propanol will be: CH3-CH(OH)-CH₃ This is a secondary alcohol because the carbon with the OH group is bonded to two alkyl groups. b. 2-methyl-2-propanol

Draw the Skeleton of 2-Methylpropane

Start by drawing 2-methylpropane, also known as isobutane, with four carbon atoms and hydrogen atoms surrounding them: CH₃ | CH₃-C-CH₃ | H

Replace One Hydrogen With the Hydroxyl (OH) Group

As this is 2-methyl-2-propanol, replace the hydrogen in the middle carbon with the OH group. The structure of 2-methyl-2-propanol will be: CH₃ | CH₃-C-OH | CH₃ This is a tertiary alcohol because there are three alkyl groups bonded to the carbon with the OH group. c. 4-isopropyl-2-heptanol

Draw the Skeleton of 4-Isopropylheptane

Start by drawing the chain of 7 carbon atoms as in heptane, then replace the hydrogen in the 4th carbon with an isopropyl group. The structure of 4-isopropylheptane will be: CH₃CH₂CH₂CH(CH₃)₂CH₂CH₂CH₃

Replace One Hydrogen With the Hydroxyl (OH) Group

Since it's 4-isopropyl-2-heptanol, replace the hydrogen in the second carbon with the OH group. The structure will be: CH₃CH(OH)CH₂CH(CH₃)₂CH₂CH₂CH₃ This is a secondary alcohol because there are two alkyl groups bonded to the carbon with the OH group. d. 2,3-dichloro-1-pentanol

Draw the Skeleton of 2,3-Dichloropentane

Draw the chain of 5 carbon atoms as in pentane and replace the hydrogen atoms in the second and third carbons with chlorine atoms. The structure of 2,3-dichloropentane will be: CH₃CH(Cl)CH(Cl)CH₂CH₃

Replace One Hydrogen With the Hydroxyl (OH) Group

Since it's 2,3-dichloro-1-pentanol, replace the hydrogen in the first carbon with the OH group. The structure will be: OH-CH(Cl)CH(Cl)CH₂CH₃ This is a primary alcohol because there is only one alkyl group bonded to the carbon with the OH group.

Key concepts

Understanding Alcohols in Organic Chemistry

Alcohols are a vital part of organic chemistry. They are defined by having one or more hydroxyl groups (-OH) attached to a carbon atom.
This functional group is what characterizes the alcohol family of compounds. Alcohols can be found in daily life in products like beverages, sanitizers, and solvents.

• The general formula for alcohols is ROH, where R represents a hydrocarbon group.
• They have different chemical properties influenced by the number of hydroxyl groups and their placement.

The functional group is key to their reactivity, allowing alcohols to participate in various chemical reactions. Each type of alcohol has different boiling points, solubility, and reactivity, which depend on its molecular structure.

Deciphering Structural Formulas

Structural formulas are a way to visualize the arrangement of atoms within a molecule. They go beyond the basic molecular formulas to provide details about how atoms are connected.

• The detailed blueprint of an alcohol includes carbon chains with attached hydroxyl groups.
• The length of the carbon chain can influence the alcohol's characteristics, such as its boiling point and solubility.

By carefully drawing the structural formula, chemists can predict the behavior and reactivity of alcohols. It helps to understand how the molecule fits in different chemical processes and how it can be manipulated in synthesis.

Exploring Functional Groups

Functional groups in molecules are specific groups of atoms that dictate the characteristics and chemical reactivity of the molecule. For alcohols, the hydroxyl group (-OH) is the primary functional group.
Functional groups are essential in defining the classes and families of different organic compounds.

• The presence and position of a functional group can change the molecule's reactivity.
• They allow chemists to classify the molecules and predict their chemical behavior.

In alcohols, the hydroxyl group lends the molecule polarity, making it more likely to engage in hydrogen bonding, influencing solubility in water.

Differentiating Primary, Secondary, and Tertiary Alcohols

Primary, secondary, and tertiary alcohols are distinguished based on the carbon atom to which the hydroxyl group is attached. These classifications affect the physical and chemical properties of the alcohol.
Here's how to distinguish them:

• Primary Alcohols: The carbon with the -OH group is attached to only one other carbon atom. An example is methanol, where the hydroxyl group is bonded to a carbon that is connected to another single carbon atom.
• Secondary Alcohols: The hydroxyl group is attached to a carbon atom that is bonded to two other carbon atoms. Isopropanol is a common secondary alcohol.
• Tertiary Alcohols: The -OH bearing carbon is bonded to three other carbon atoms. An example is tert-butanol.

Recognizing these differences helps predict reactivity and potential uses in chemical synthesis and industrial applications.