Answer to Question #32530 in Organic Chemistry for Mohamad

Question

hi
can you help me to determine a material or indicator that it specify the 2ethylhexanol content in Dioctyl phthalate (dop) sample.
please advice me.
thank you very much.
shahbazi

Answer 1

DEHP is produced by the esterfication of phthalic anhydride with 2-ethyl-hexanol. This reaction occurs in two successive steps. The first reaction step results in the formation of monoester by alcoholysis of phthalic acid. This step is rapid and proceeds to completion. The second step involves the conversion of the monoester to the di-ester. This is a reversible reaction and proceeds more slowly than the first. To shift the equilibrium towards the di-ester, the reaction water is removed by distillation. Excess alcohol is recovered and recycled and DEHP is purified by vacuum distillation and/or activated charcoal. The reaction sequence is performed in a closed system. This process can be run continuously or batchwise.

The percentage of alcohol in solution (and thus the "proof") is usually determined using a hydrometer, a device that measures the density (or the specific gravity to be more precise) of the solution. As the percentage of alcohol in a solution increases, the density decreases because alcohol has a lower density that water. The hydrometer is a floating device that has a long stem that sticks out of the solution. As the density of the solution decreases the hydrometer sinks further into the liquid. The amount of the stem that sticks out of the solution is a measure of the percentage of alcohol or the proof - the more of the stem that sticks out of the solution, the lower the "proof".