3- Pentanone, boiling point

Both 2-pentanone and 3-pentanone have boiling points of 102°C. How can the two ketones be distinguished (refer to Table 31.4) ... 

The boiling points of the isomeric carbonyl compounds heptanal, 4-heptanone, and 2,4-dimethyl-3-pentanone are 155°C, 144°C, and 124°C, respectively. Suggest a possible explanation for the observed order. Hint Recall the effect of chain branching on the boiling points of isomeric alkanes, and how steric effects can influence the association of the molecules.)... 

Synonynu Diacetone 4-Hydroxy-4-Metrhyl-2-Pentanone Tyranton Chemical Formula CHjC(OH)(CH3)-CH2C(XH3 (ii) Observable Characteristics — Physical State (as normally shipped) Liquid Color Colorless to yellow Odor Mild, pleasant (iii) Physical and Chemical Properties — Physical State at 15 "C and 1 atm. Liquid Molecular Weight 116.16 Boiling Point at I atm. 336.6, 169.2, 442.4 Freezing Point -45.0, -42.8, 230.4 Critical Temperature 633, 334, 607 Critical Pressure 380, 36, 3.6 Specific Gravity 0.938 at 20°C (liquid) Vapor (Gas) Density Not pertinent Ratio of Specific Heats... 

The boiling points of 3-hydroxy-2-pentanone and 5-hydroxy-2-pentanone are 147 and 210 °C, respectively. Suggest a reason for this difference. 

As a consequence, the extent of intermolecular hydrogen bonding is decreased. Decreased intermolecular hydrogen bonding allows molecules to escape more readily and lowers the boiling point. The probability of an intramolecular hydrogen bond in 5-hydroxy-2-pentanone is far less than in 3-hydrox-yl-2-pentanone because a seven-membered ring would be required. 

The aqueous layer is separated and extracted with 4-methyl-2-pentanone. The combined organic layer are dried over MgS04 and evaporated. The oily residue is dissolved in a mixture of 24 parts diisopropylether and 24 parts isopropanol. After cooling overnight to -20°C, 5.3 parts product are obtained. This crop is boiled in 72 parts 4-methyl-2-pentanone and cooled to 0°C, yielding l-(3-cyano-3,3-diphenylpropyl)-4-(2-oxo-l-benzimidazolinyl) piperidine, melting point 225-226°C, as a grey-white amorphous powder. 

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