Boiling Point for Common Organic Solvents

Table 4.5B Boiling Points for Common Organic Solvents...

Table 4.5C Boiling Point for Common Organic Solvents Arranged...

TABLE 4.5C Boiling Points for Common Organic Solvents (compound type in order of increasing boiling point... 

In comparison to the high enthalpy of evaporation of water (57.36 kj moh1), the respective values are much lower for organic solvents, which are thus much easier to separate than water. Table 12.1 lists some boiling points and enthalpies of evaporation for common organic solvents. 

Table 12.1 Boiling points and enthalpies of evaporation for common organic solvents.

The solvothermal method is more efficient and permits wide range of reaction temperature due to high boiling point of the organic solvents. The most common method rmder solvothermal is hot-injection method compared to heating-up method used for colloidal synthesis of nanocrystals. 

Nitrobenzene is an extremely versatile solvent, and may frequently be employed for the crystallisation of compounds which do not (hssolve appreciably in the common organic solvents. The vapour is somewhat poisonous, so that recrystallisations must be carried out in the fiune cupboard. After the crystals have been collected, they should be washed with a volatile solvent, such as benzene, alcohol or ether, to remove the excess of nitrobenzene (compare Section 11,32). The only disadvantage of nitrobenzene as a solvent is that it has a pronounced oxidising action at the boiling point. 

Acetone is the most important commercial ketone, with over 3 billion kilograms used each year. Both acetone and methyl ethyl ketone (butan-2-one) are common industrial solvents. These ketones dissolve a wide range of organic materials, have convenient boiling points for easy distillation, and have low toxicities. 

For liquid-liquid extraction, water is usually the polar solvent. Since most extractions involve getting the required compound into the organic solvent (or removing unwanted ionic chemicals from it), it should have good solvent power for the desired compound and a low boiling point for ease of removal and recovery of the compound. The common organic solvents used in liquid-liquid extraction are diethyl ether (ethoxyethane) b.pt. 34 °C, dichloromethane (DCM) b.pt. 41 °C and ethyl acetate (ethyl ethanoate) b.pt. 77 °C. Dichloromethane is denser than water and forms the lower layer, whereas diethyl ether and ethyl acetate float on water and are the upper layer. 

Using a simple, sealed, microwave transparent apparatus (e.g.. Teflon or glass), it is possible to rapidly increase the temperature of a reaction in common organic solvents up to 100°C above the conventional boiling point of the solvent, which leads to a thousand-fold acceleration of the reaction rate. For example, methanol, which has a boiling point of 65°C, can be rapidly heated to 160°C and a pressure of 17 atmospheres. 

---