Procedure #4 (Source: J. Org. Chem. 2017, 82, 1114-1126.) Start with 5 g of benz

ID: 495749 • Letter: P

Question

Procedure #4 (Source: J. Org. Chem. 2017, 82, 1114-1126.) Start with 5 g of benzoic acid as "the benzoic acid 5. General Procedures for the Synthesis of Weinreb Amides from Corresponding Acids 20 In a two-neck round-bottomed flask was added oxaly de (1.2 equiv) dropwise into the stirring solution of the berzoic acid (i equiv) in C1 Cl2 at 0 a C. This was followed by addition of DMF (2 drops). The reaction mixture was allowed to wart: to root: temperature and stirred for another 1.5 h and then recooled to o C. Et N (3 equiv) and NO-dimethylhydroxyl- amine hydrochloride (I os equiv were added. The reaction mixture was once again allowed :o warm to room temperature and stirred for a further 6 h. I: was cuenched at room ter perature with a saturated solution o Nal CO" and the resulting mixture was extracted twice wi: CI The combined organic extracts were washed with brine and dried over anhydrous Nazsos, filtered, and concentrated under vacuur: The crude product was purified by silica gel flash column chromatography.

Explanation / Answer

Substance

Mol. Wt.

Wt. Or Vol.

mmol

Equivalent

Benzoic acid

122.123 g/mol

5 g

40.9423

Oxalyl chloride

126.93 g/mol

6.2361 g (4.22 ml)

49.1307

1.2

TEA

101.19 g/mol

12.4292 g (17.13 ml)

122.83

N,O-DimethylhydroxylamineHCl

97.54 g/mol

4.1932 g

42.9894

1.05

Moles = weight (mass) / molecular weight

Density = Weight (mass) / Volume

Benzoic acid Moles = Wt / mol. Wt. = 5 / 122.123 = 40.9423 mmol

1 mol of Oxalylchloride = 126.93 g

49.1307 mmol Oxalylchloride = 49.1307 mmol * 126.93 g = 6.2361 g = 6.2361 g / 1.4785 g/ml (density of OC) = 4.22 ml

122.83 mmol of TEA = 0.12283 * 101.19 = 12.4292 g of TEA = 12.4292 g / (0.7255 g/ml) = 17.13 ml of TEA

N,O-Dimethylhydroxylamine hydrochloride

0.0429894 mol of N,O-Dimethylhydroxylamine hydrochloride = 0.0429894 * 97.54 = 4.1932 g