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f) The physical properties of alkynes are very similar to those of alkenes and alkanes with the same number of carbons. Therefore 1-butene and 1-butyne will have very similar boiling points. g) 1-Pentanol is higher boiling because it can hydrogen bond. h) Cyclopentanol and cyclopentylamine are both polar, both can form hydrogen bonds, and they have similar molecular masses. However, because oxygen is more electronegative than nitrogen, cyclopentanol forms stronger hydrogen bonds. Therefore, cyclopentanol has a higher boiling point (141°C) than cyclopentylamine (108°C). 5.38 When two immiscible liquids are mixed together, the denser liquid forms the lower layer. Chloroform is denser than water because of its more massive chlorine atoms, so it forms the lower layer. 5.39 Remember, like dissolves like. Water is very polar and can hydrogen bond, so more polar compounds and compounds capable of hydrogen bonding will be more soluble in water. a) 1-Butanol has a higher solubility in water because it is more polar and can form more hydrogen bonds. b) 1-Butanol has a higher solubility in water because it has a smaller nonpolar hydrophobic hydrocarbon chain than 1-hexanol. c) Diethylamine is more soluble in water than pentane because it is polar and can hydrogen bond with water. Pentane is nonpolar and therefore hydrophobic. 5.40 Amines often have unpleasant, fishy odors. Therefore it is possible that the fishy smelling unknown compound is an amine. Amines are bases, so they react with strong acids to form water soluble salts. Testing the solubility of the unknown compound in dilute aqueous hydrochloric acid is one way of confirming the presence of the amine functional group. 5.41 Turpentine should not mix with water because it is composed of nonpolar hydrocarbons. If a paint dissolves in turpentine, the paint is also composed of nonpolar molecules. 5.42 A higher the ratio of C and H to results in a compound with a higher energy content. A fat has a lower ratio of C and H to O than an alkane, but a higher ratio than ethanol, so its energy content should be between the values for these compounds. 76