Separation The first step in your procedure should be to dissolve about 0.5 g (r

Question

Separation The first step in your procedure should be to dissolve about 0.5 g (record exact weight) of the mixture in the minimum amount of diethyl ether or methylene chlo- ride. If more than about 4 ml of a solvent is required, you should use the other sol- vent. Most of the compounds in the mixtures are more soluble in methylene chloride than diethyl ether; however, you may need to determine the appropriate solvent by experimentation. Once you have selected a solvent, this same solvent should be used throughout the procedure when an organic solvent is required. If you use di- ethyl ether, you must use two steps to dry the organic layer. First, the organic layer must be mixed with saturated sodium chloride (see Technique 12, Section 12.9, Saturated Salt Solution), and then the liquid is dried over granular anhydrous so- dium sulfate. (see Technique 12, Section 12.9, Drying Procedure with Anhydrous Sodium Sulfate). Your mixture may be one of the following: (1) 50% benzoic acid, 40% benzoin, 10% 1,4-dibromobenzene; (2) 50% fluorene, 40% o-toluic acid, 10% 1,4-dibromobenzene; (3) 50% phenanthrene, 40% methyl 4-aminobenzoate, 10% 1,4-dibromobenzene; or (4) 50% 4-aminoacetophenone, 40% 1,2,4,5-tetrachlorobenzene, 10% 1,4-dibromobenzene. Other mixtures are given in the Instructor's Manual, along with some suggestions about these mixtures. © 2013 Ceangage Learning, All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part 46 A Microscale Approach to Organic Laboratory Techniques Sie Pavia, Lampman, Kriz, Engel Purification To improve the purity of your final samples, it may be helpful to include a backwashing step at the appropriate place in your procedure. See Technique 12, Section 12.11, for a discussion of this technique. Crystallization will likely be required to purify both of the compounds you isolate. To find an appropriate solvent, you should consult a handbook. You can also use the procedure in Technique 12, Section 11.6, to determine a good solvent experimentally. Note that dioluulothor or othoraron las hniline malente a un nest vanavaller anna nalerunden for

Explanation / Answer

methyl 4-aminobenzoate is organic base in nature; In the reaction mixture to separte the base from neutral compounds (phenanthrone & 1,4-dibromobenzene) as you are trying by acid base treatment please acidify the reaction mixture to pH 1 using 1 N HCl and extract with organic solvents like you have tried with methlyene chloride or other solvents ethyl acetate, chloroform or diethyl ether. The two neutral compounds (phenanthrone & 1,4-dibromobenzene) comes into the organic layer and methyl 4-aminobenzoate (due to acidify the reaction mixture with dil HCl it will form HCl salt and will go into the aqeous phase) will go in the water layer. After seprtion of organic layer and aqeous layer by separting funnel, the Organic layer, once you evapourated under rota vapour you will get misture of two neutral compounds that is phenanthrone & 1,4-dibromobenzene.

The aquous layer you have sepeated from organic layer, basify with 1N NaOH to neutral pH (to bring the methyl 4-aminobenzoate.HCl salt to amino form) and then extract with organic solvents like dichloromethane, diethylether, chloroform or ethyl acetate and then evapoured under reduced pressure (rotavapour) will get the pure form of methyl 4-aminobenzoate.

To separate the two neutral compounds obtained from first time organic layer, evapourate the organic solvent then the obtained mixture of two neutral compunds ( phenanthrone & 1,4-dibromobenzene)can be separted either by column chromatography or . or by fractional distillation (applying vacuum); 1,4-dibromobenzene boiling point is 220 0C, Theoretical yields can be caluculate based on the reactants weights or moles used in the reaction.

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