CHEM 3221 Chapter Notes - Chapter 4: Activated Carbon, Seed Crystal, Boiling Point

• School: University of Houston
• Department: Chemistry
• Course: CHEM 3221
• Professor: Bean Mary

Document Summary

Recrystallization: purification process used to remove impurities from organic compounds that are solid at room temperature. Solubility of the compounds decreases as the solution cools, and crystals form. The compound to be crystallized should be insoluble at room temperature and soluble near the sol(cid:448)e(cid:374)t"s (cid:271)oili(cid:374)g poi(cid:374)t. Impurities should be soluble in the chosen solvent at all temperatures so that impurities stay in solution. Polar organic molecules have groups that form hydrogen bond, such as -oh, -nh2, -co2h. If the sol(cid:448)e(cid:374)t"s (cid:271)oili(cid:374)g poi(cid:374)t is higher tha(cid:374) the (cid:272)o(cid:373)pou(cid:374)d"s (cid:373)elti(cid:374)g poi(cid:374)t, the (cid:272)o(cid:373)pou(cid:374)d (cid:449)ill oil out. Oiling out: when a compound is insoluble in a solution at the temperature above the (cid:272)o(cid:373)pou(cid:374)d"s (cid:373)elti(cid:374)g poi(cid:374)t, the (cid:272)o(cid:373)pou(cid:374)d is deposited as a(cid:374) oil, a(cid:374)d (cid:374)ot as (cid:272)rystals. An abundant quantity of crystals must be recoverable from the cool solvent. Solvent pair: two solvents are selected that are miscible to each other but have opposite abilities to dissolve the compound.