Hydroxyl Group

Definition

The hydroxyl group (–OH) is a functional group consisting of an oxygen atom covalently bonded to a hydrogen atom. It is an important structural component in organic chemistry, particularly in the study of alcohols and ethers.

5 Must Know Facts For Your Next Test

1. The hydroxyl group is polar due to the unequal sharing of electrons between the oxygen and hydrogen atoms, which gives it a partial positive and partial negative charge.
2. Alcohols, which contain a hydroxyl group, are classified based on the number of carbon atoms the hydroxyl group is attached to (primary, secondary, or tertiary).
3. Ethers are organic compounds that contain an oxygen atom connected to two alkyl or aryl groups, and they do not contain a hydroxyl group.
4. The hydroxyl group can participate in hydrogen bonding, which affects the physical and chemical properties of alcohols and ethers, such as boiling point and solubility.
5. The presence of the hydroxyl group in alcohols and ethers can influence their reactivity, allowing them to undergo various chemical transformations, such as oxidation, substitution, and elimination reactions.

Review Questions

• Explain the polarity of the hydroxyl group and how it contributes to the properties of alcohols and ethers.
  • The hydroxyl group (–OH) is polar due to the unequal sharing of electrons between the oxygen and hydrogen atoms. This polarity gives the hydroxyl group a partial positive charge on the hydrogen and a partial negative charge on the oxygen. This polarity allows the hydroxyl group to participate in hydrogen bonding, which affects the physical and chemical properties of alcohols and ethers, such as their boiling points, solubility, and reactivity. For example, the ability of alcohols to form hydrogen bonds with water molecules contributes to their high boiling points and solubility in polar solvents.
• Differentiate between the structures and properties of alcohols and ethers, and explain the role of the hydroxyl group in each.
  • Alcohols are organic compounds that contain a hydroxyl group (–OH) attached to a saturated carbon atom, while ethers are organic compounds that contain an oxygen atom connected to two alkyl or aryl groups and do not contain a hydroxyl group. The presence of the hydroxyl group in alcohols allows them to participate in hydrogen bonding, which influences their physical and chemical properties, such as their higher boiling points and solubility in polar solvents compared to ethers. In contrast, the absence of a hydroxyl group in ethers means they do not participate in hydrogen bonding, resulting in lower boiling points and reduced solubility in polar solvents.
• Evaluate the role of the hydroxyl group in the reactivity of alcohols and ethers, and predict the types of reactions they may undergo.
  • The hydroxyl group in alcohols plays a crucial role in their reactivity, as it can undergo various chemical transformations, such as oxidation, substitution, and elimination reactions. For example, the hydroxyl group can be oxidized to form aldehydes, ketones, or carboxylic acids. Additionally, the hydroxyl group can participate in substitution reactions, where the hydrogen atom is replaced by other functional groups. In contrast, ethers, which lack the hydroxyl group, are generally less reactive and tend to undergo fewer transformations compared to alcohols. The absence of the hydroxyl group in ethers means they are less susceptible to oxidation and substitution reactions, and they are often used as solvents or as intermediates in organic synthesis due to their relatively inert nature.

Related terms

Alcohol: An organic compound containing a hydroxyl group (–OH) attached to a saturated carbon atom.

Ether: A class of organic compounds that contain an oxygen atom connected to two alkyl or aryl groups.

Hydrogen Bonding:

An intermolecular attractive force that occurs between a hydrogen atom bonded to a highly electronegative atom (such as oxygen, nitrogen, or fluorine) and another highly electronegative atom.