Iodoform melting point

Methylene iodide is a very heavy, highly refractive liquid, which darkens on exposure to light, air, and moisture. It has a melting point of 6 Celsius, and a boiling point of 181 Celsius. Methylene iodide is insoluble in water, but is miscible with alcohol, hexane, cyclohexane, ether, chloroform, and benzene. It dissolves sulfur and phosphorus. Methylene iodide is prepared by reacting iodoform with sodium arsenite, or by heating iodoform with sodium acetate in 95% ethanol. 

You will be given an unknown that may be any of the aldehydes or ketones listed in Table 1. At least one derivative of the unknown is to be submitted to the instructor but if you first do the bisulfite and iodoform characterizing tests, the results may suggest derivatives whose melting points will be particularly revealing. 

Iodoform can be recognized by its odor and yellow color and, more securely, from the melting point (119-123°C). The substance can be isolated by suction filtration of the test suspension or by adding 0.5 mL of dichloromethane, shaking the stoppered test tube to extract the iodoform into the small lower layer, withdrawing the clear part of this layer with a Pasteur pipette, and evaporating it in a small tube on the steam bath. The crude solid is crystallized from methanol-water. 

Hypoiodites are used for qualitative tests for methyl ketones (Lieben test). For this purpose, a compound to be tested is stirred with an aqueous solution of sodium hydroxide (80 mol/mol of methyl ketone). Iodine (4.5 mol of 12) is added portionwise with stirring, and the mixture is set aside for 20 min at 25 °C before acidification. In the presence of a methyl keto group, a yellow heavy precipitate of iodoform settles at the bottom of the test tube. Iodoform can be identified easily not only by its characteristic smell but also by its melting point (120-123 °C) [1173], This test applies not only to methyl ketones but to any compound that can be converted in the reaction medium into a species containing the COCH3 group, for example, isopropyl or ethyl alcohol. 

Iodoform org chem CHI3 A yellow, hexagonal solid melting point 119°C soluble in chloroform, ether, and water has weak bactericidal qualities and is used in ointments for minor skin diseases. Also known as triiodomethane. T o-da.form lodohydrocarbon org chem A hydrocarbon in which an iodine atom replaces one or more hydrogen atoms In the molecule, as in an alkane, aromatic, or olefin. T o-da.hT-dra kar-bcn ... 

Procedure To the sample (100 mg) dissolved in 1 ml of water (insoluble substances should be dissolved in methaaol or dioxane) are added 3 ml of 10% NaOH and then, dropwise, a 10% iodine solution in 20% aqueous potassium iodide until it is in excess. The test tube is then immersed in water at 60 °C. Additional iodine solution is added until its color persists for 2 min followed by dropwise addition of alkali until the brown color fades. The test tube is taken out of the water bath and 10 ml of water are added to it. Iodoform separates as a yellow solid of characteristic odor, the melting point of which is 120 °C. If the separated iodoform is not lemon-yellow, it is separated by filtration, suspended in 2 —3 ml of dioxane, and shaken with 1 ml of 10% NaOH. 

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