The Physical Properties of Carbonyl Compounds

The acid properties of carboxylic acids were discussed in Sections 2.3 and 8.15. Recall that carboxylic acids have pA a values of approximately 5. Carbonyl compounds have the following relative boiling points  

Carboxylic acid derivatives are soluble in solvents such as ethers, chloroalkanes, and aromatic hydrocarbons. Like alcohols and ethers, carbonyl compounds with fewer than four carbons are soluble in water. Tables of physical properties can be found in the Study Area of MasteringChemistry. 

Esters, A,A -disubstituted amides, and nitriles are often used as solvents because they are polar but do not have reactive OH or NH2 groups. We have seen that dimethylformamide (DMF) is a common aprotic polar solvent (Section 9.2). 

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The polarity of the carbonyl group is manifest in the physical properties of carbonyl compounds. Boiling points for the lower members of a series of aldehydes and ketones are 50-80° higher than for hydrocarbons of the same molecular weight this may be seen by comparing the data of Table 16-2 (physical... 

In addition to its effect on reactivity, polarization of the C=0 bond influences the physical properties of carbonyl compounds. For example, carbonyl compounds boil at higher temperatures than hydrocarbons, but at lower temperatures than alcohols of comparable molecular weight. 

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