Functional groups, when attached to various hydrocarbons, increase the reactivity and water solubility of the hydrocarbon. Carboxylic acids and phenols are the only organic acids; they are weak acids. Amines are the only significant organic bases. All functional groups that contain a hydrogen connected to a nitrogen or oxygen atom have the ability to form hydrogen bonds between themselves. All functional groups that contain a nitrogen or oxygen atom can form hydrogen bonds with water, which increase their solubility. In general, organic compounds of low molecular weight (less than five carbons) which contain functional groups, are soluble in water. Table 3-3 summarizes the properties and some reactions of the organic compounds we have studied.