The hydroxyl group (OH-) is a functional group consisting of an oxygen atom covalently bonded to a hydrogen atom. It is a key structural feature in many organic compounds, particularly alcohols and phenols, and plays a crucial role in their chemical properties and reactivity.
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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.
Alcohols and phenols containing the hydroxyl group can participate in hydrogen bonding, which influences their physical and chemical properties, such as boiling points, solubility, and reactivity.
The hydroxyl group can undergo various reactions, including substitution, elimination, and oxidation, which are important in the synthesis and transformation of organic compounds.
The presence of the hydroxyl group in halohydrins (8.3) and the hydration of alkenes (8.5) allows for the formation of alcohols, which are important intermediates in organic synthesis.
The hydroxyl group is a key feature in the naming and classification of alcohols and phenols (17.1), and it influences their physical and chemical properties (17.2).
Review Questions
Explain the role of the hydroxyl group in the formation of halohydrins from alkenes.
In the addition of HO-X to alkenes (8.3 Halohydrins from Alkenes: Addition of HO-X), the hydroxyl group (-OH) is added to one carbon of the alkene, while the halogen (X) is added to the other carbon. This results in the formation of a halohydrin, which is an important intermediate in organic synthesis that can be further transformed into other useful compounds.
Describe how the hydroxyl group influences the hydration of alkenes through the process of hydroboration-oxidation (8.5 Hydration of Alkenes: Addition of H2O by Hydroboration).
In the hydration of alkenes by hydroboration-oxidation, the initial step involves the addition of borane (BH3) to the alkene, forming a trialkylborane intermediate. The subsequent oxidation step then introduces the hydroxyl group (-OH) to the carbon atom that was previously bonded to the boron, resulting in the formation of an alcohol. The presence of the hydroxyl group is crucial in this transformation, as it allows for the conversion of the alkene into a more functionalized alcohol product.
Analyze the role of the hydroxyl group in the naming, properties, and reactions of alcohols and phenols (17.1 Naming Alcohols and Phenols, 17.2 Properties of Alcohols and Phenols, 17.4 Alcohols from Carbonyl Compounds: Reduction, 17.9 Phenols and Their Uses, 17.10 Reactions of Phenols).
The hydroxyl group (-OH) is the defining feature of alcohols and phenols, and its presence significantly influences their nomenclature, physical and chemical properties, and reactivity. The position and number of hydroxyl groups are used to name these compounds, while the polarity and hydrogen bonding ability of the hydroxyl group impact their boiling points, solubility, and reactivity. Alcohols can be synthesized by the reduction of carbonyl compounds, and both alcohols and phenols undergo various reactions, such as oxidation, esterification, and substitution, which are important in organic synthesis and the production of useful compounds. The hydroxyl group is a versatile functional group that is central to the understanding and manipulation of these important organic compounds.
A strong intermolecular force that occurs between a hydrogen atom covalently bonded to a highly electronegative atom, such as oxygen, and another highly electronegative atom.