Note
Esters are common solvents. Ethyl acetate is used to extract organic solutes from aqueous solutions—for example, to remove caffeine from coffee. It also is used to remove nail polish and paint. Cellulose nitrate is dissolved in ethyl acetate and butyl acetate to form lacquers. The solvent evaporates as the lacquer “dries,” leaving a thin film on the surface. High boiling esters are used as softeners (plasticizers) for brittle plastics.
Table 15.4 Physical Properties of Some Esters | |||||
---|---|---|---|---|---|
Condensed Structural Formula | Name | Molar Mass | Melting Point (°C) | Boiling Point (°C) | Aroma |
HCOOCH3 | methyl formate | 60 | −99 | 32 | |
HCOOCH2CH3 | ethyl formate | 74 | −80 | 54 | rum |
CH3COOCH3 | methyl acetate | 74 | −98 | 57 | |
CH3COOCH2CH3 | ethyl acetate | 88 | −84 | 77 | |
CH3CH2CH2COOCH3 | methyl butyrate | 102 | −85 | 102 | apple |
CH3CH2CH2COOCH2CH3 | ethyl butyrate | 116 | −101 | 121 | pineapple |
CH3COO(CH2)4CH3 | pentyl acetate | 130 | −71 | 148 | pear |
CH3COOCH2CH2CH(CH3)2 | isopentyl acetate | 130 | −79 | 142 | banana |
CH3COOCH2C6H5 | benzyl acetate | 150 | −51 | 215 | jasmine |
CH3CH2CH2COO(CH2)4CH3 | pentyl butyrate | 158 | −73 | 185 | apricot |
CH3COO(CH2)7CH3 | octyl acetate | 172 | −39 | 210 | orange |
Concept Review Exercises
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Which compound has the higher boiling point: CH3CH2CH2CH2OH or CH3COOCH3? Explain.
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Which compound is more soluble in water—methyl propanoate or butyric acid? Explain.
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Key Takeaways
- Esters have polar bonds but do not engage in intermolecular hydrogen bonding and are therefore intermediate in boiling points between the nonpolar alkanes and the alcohols, which engage in intermolecular hydrogen bonding.
- Ester molecules can engage in hydrogen bonding with water, so esters of low molar mass (3-5 C atoms) are somewhat soluble in water.
Exercises
- Which compound has the higher boiling point: CH3CH2CH2COOH or CH3CH2CH2COOCH3? Explain.
- Which compound is more soluble in water—methyl acetate or octyl acetate? Explain.
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