Lidocaine bisulfate

Analysis Weigh the lidocaine bisulfate and calculate its yield. Determine its melting point (reported mp, 210-212 °C). Caution Do nofuse a liquid-bath melting-point apparatus to determine the melting point use a metal block apparatus, as illustrated in Figure 2.19, Section 2.7.) Obtain IR and NMR spectra of your product and compare them with those of an authentic sample (Figs. 21.28-21.29). 

Given the yields that you obtained in the laboratory, calculate the number of moles of 2,6-dimethylnitrobenzene (35) that would be needed to prepare one mole of lidocaine bisulfate (42). 

Consider the spectral data for lidocaine bisulfate (Figs. 21.28 and 21.29). 

Discuss the differences observed in the IR and NMR spectra of a-chloro-2, 6-dimethylacetanilide and lidocaine bisulfate that are consistent with the formation of the latter in this procedure. 

Isolation of 25 involves filtering the reaction mixture to remove the diethylammonium hydrochloride, followed by extraction of the basic 25 into aqueous hydrochloride. All nonbasic contaminants, such as unchanged 37, remain in the toluene solution. Lidocaine is liberated from its hydrochloride acid salt with aqueous base and then extracted into diethyl ether. After removal of the diethyl ether, the lidocaine is isolated as a low-melting solid or oil, depending upon its purity. In order to facilitate purification of lidocaine in this procedure, it is converted into its solid bisulfate salt 42 by reaction with sulfuric acid (Eq. 21.24). Many drugs that contain a basic site, like lidocaine, are sold in the form of their hydrochloride or sulfate salts because these salts are typically more stable and more soluble in water than the free base. 

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