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Two key ingredients found in many soaps are PEG 150 distearate and ethylhexyl glycerin. Both can be synthesized from glyceryl tristearate (Figure 1) .
Figure 1 Formation of PEG 150 distearate and ethylhexyl glycerin from glyceryl tristearateThe first step in this process requires the saponification of glyceryl tristearate. The resulting stearate molecules can then react with PEG 150 in an acid-catalyzed Fischer esterification to form PEG 150 distearate. The glycerol produced during saponification is used as a nucleophile to form ethylhexyl glycerin through a base-catalyzed S_N2 reaction with an ethylhexyl halide.Studies have shown that hand washing with soap can substantially reduce the number of germs present on hands and that washing hands before preparing food is particularly effective in reducing illness. Researchers examined the effect of washing for 20 seconds with different amounts of soap containing PEG 150 distearate and ethylhexyl glycerin and found an inverse correlation between the volume of soap used and the amount of bacteria recovered from the hands. The data are shown in Figure 2.
Figure 2 Bacteria recovered from hands after washing with varying amounts of soapThe researchers then investigated the effect of hand washing with different kinds of soap on the transfer of bacteria from hands to objects. Volunteers washed with a fixed volume of soap for 30 seconds, then handled sterilized plastic spheres for 30 seconds. Bacteria were then recovered from the spheres. The results are shown in Table 1.Table 1 Bacteria Recovered from Objects
Adapted from Fuls JL, Rodgers ND, Fischler GE, et al. Alternative hand contamination technique to compare the activities of antimicrobial and nonantimicrobial soaps under different test conditions. Appl Environ Microbiol. 2008.
-A reaction between a long-chain anhydride and phenylethylamine is done to produce a long-chain amide and a carboxylic acid. Which of the following aqueous solutions can separate the products of this reaction in an extraction?

Question

Passage
Two key ingredients found in many soaps are PEG 150 distearate and ethylhexyl glycerin. Both can be synthesized from glyceryl tristearate (Figure 1) .

Figure 1 Formation of PEG 150 distearate and ethylhexyl glycerin from glyceryl tristearateThe first step in this process requires the saponification of glyceryl tristearate. The resulting stearate molecules can then react with PEG 150 in an acid-catalyzed Fischer esterification to form PEG 150 distearate. The glycerol produced during saponification is used as a nucleophile to form ethylhexyl glycerin through a base-catalyzed S_N2 reaction with an ethylhexyl halide.Studies have shown that hand washing with soap can substantially reduce the number of germs present on hands and that washing hands before preparing food is particularly effective in reducing illness. Researchers examined the effect of washing for 20 seconds with different amounts of soap containing PEG 150 distearate and ethylhexyl glycerin and found an inverse correlation between the volume of soap used and the amount of bacteria recovered from the hands. The data are shown in Figure 2.

Figure 2 Bacteria recovered from hands after washing with varying amounts of soapThe researchers then investigated the effect of hand washing with different kinds of soap on the transfer of bacteria from hands to objects. Volunteers washed with a fixed volume of soap for 30 seconds, then handled sterilized plastic spheres for 30 seconds. Bacteria were then recovered from the spheres. The results are shown in Table 1.Table 1 Bacteria Recovered from Objects

Adapted from Fuls JL, Rodgers ND, Fischler GE, et al. Alternative hand contamination technique to compare the activities of antimicrobial and nonantimicrobial soaps under different test conditions. Appl Environ Microbiol. 2008.
-A reaction between a long-chain anhydride and phenylethylamine is done to produce a long-chain amide and a carboxylic acid. Which of the following aqueous solutions can separate the products of this reaction in an extraction?

Quizplus · Accepted Answer

11ecba2d_1269_2d33_a3bf_399c856dae52_MD0008_00 Acylation reactions between anhydrides and amines generate amides and carboxylic acids. Amides and carboxylic acids are polar, water-soluble molecules because they form hydrogen bonds in an aqueous solution. However, long alkyl side chains (R groups) of amides and carboxylic acids increase the hydrophobic (nonpolar) nature of the molecules and make them insoluble in aqueous solvents. Long-chain amides and carboxylic acids are the products of the reaction between long-chain anhydrides and the amine group of phenylethylamine. To separate long-chain amides from carboxylic acids in the organic layer, a base must be added. Bases deprotonate the carboxylic acid and generate carboxylate anions that are more soluble in the aqueous layer than in the organic layer. Dilute LiOH is strong enough to deprotonate a carboxylic acid but not to deprotonate an amide N-H. Therefore, addition of the base LiOH will produce carboxylate anions that enter the aqueous layer and allow long-chain amides to remain in the organic layer. (Choice A) NaHSO₄ (pK_b ∼12) is not basic enough to deprotonate the carboxylic acid. NaHSO₄ is the salt of the conjugate base of sulfuric acid (a strong acid), and strong acids produce weak conjugate bases. (Choices B and D) HNO₃ and HClO₄ are both acids. Acids will not deprotonate carboxylic acids, and therefore cannot be used to separate long-chain amides and carboxylic acids. Educational objective: Acylation reactions between anhydrides and amines generate amides and carboxylic acids. The solubility of carboxylic acids in water increases when they are converted into carboxylate anions by a base.

Passage Two Key Ingredients Found in Many Soaps Are PEG 150