Alcohols and Phenols
Properties of Alcohols and Phenols Experiment #3
Objectives: To observe the solubility of alcohols relative to their chemical structure, to perform chemical tests to distinguish primary, secondary and tertiary alcohols, and a color test for phenol. Introduction The general formula of an alcohol is ROH in which the R is an aliphatic hydrocarbon group. Alcohols may be looked upon as derivatives of water, HOH. One hydrogen of water is substituted by an alkyl group, R. Like water, alcohols show hydrogen bonding. As the chain of the R group increases the hydrocarbon character of the compound overshadows the polar character of the OH group. Consequently, the solubility and boiling point of an alcohol are affected by the length of the carbon chain and the shape of the molecule. The short chain alcohols are soluble in water, whereas the longer chain alcohols are insoluble in water. In general a molecule which is more compact (i.e., more branched) will be more soluble in water and will have a lower boiling point than the straight chain isomer. Phenols are aromatic alcohols, in which R is an aromatic ring. This experiment will demonstrate some of the properties of alcohols and phenols. Although alkyl alcohols have an -OH group, they do not ionize in water, whereas phenols ionize like acids (donating a proton to water). The -OH group of alkyl alcohols can be positioned on different carbon atoms of the carbon chain and are classified as primary (1°), secondary (2°), or tertiary (3°) alcohols depending on whether the -OH group is attached to a carbon with 1, 2 or 3 other carbon atoms attached to it. These different alcohols react differently with Lucas reagent and with Bordwell-Wellman reagent; hence these reagents can be used for identifying the class of alcohol. The relative acidity of phenols can be used to characterize this class of alcohols relative to the alkyl alcohols. This property will be exploited in the identification of phenol.
Materials Test tubes,
Objectives: To observe the solubility of alcohols relative to their chemical structure, to perform chemical tests to distinguish primary, secondary and tertiary alcohols, and a color test for phenol. Introduction The general formula of an alcohol is ROH in which the R is an aliphatic hydrocarbon group. Alcohols may be looked upon as derivatives of water, HOH. One hydrogen of water is substituted by an alkyl group, R. Like water, alcohols show hydrogen bonding. As the chain of the R group increases the hydrocarbon character of the compound overshadows the polar character of the OH group. Consequently, the solubility and boiling point of an alcohol are affected by the length of the carbon chain and the shape of the molecule. The short chain alcohols are soluble in water, whereas the longer chain alcohols are insoluble in water. In general a molecule which is more compact (i.e., more branched) will be more soluble in water and will have a lower boiling point than the straight chain isomer. Phenols are aromatic alcohols, in which R is an aromatic ring. This experiment will demonstrate some of the properties of alcohols and phenols. Although alkyl alcohols have an -OH group, they do not ionize in water, whereas phenols ionize like acids (donating a proton to water). The -OH group of alkyl alcohols can be positioned on different carbon atoms of the carbon chain and are classified as primary (1°), secondary (2°), or tertiary (3°) alcohols depending on whether the -OH group is attached to a carbon with 1, 2 or 3 other carbon atoms attached to it. These different alcohols react differently with Lucas reagent and with Bordwell-Wellman reagent; hence these reagents can be used for identifying the class of alcohol. The relative acidity of phenols can be used to characterize this class of alcohols relative to the alkyl alcohols. This property will be exploited in the identification of phenol.
Materials Test tubes,