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.
-Which additional extraction steps would cause phosphatidylethanolamine and 2,6-dimethoxyphenol to enter the aqueous layer consecutively?

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.
-Which additional extraction steps would cause phosphatidylethanolamine and 2,6-dimethoxyphenol to enter the aqueous layer consecutively?

Quizplus · Accepted Answer

11ecba2d_1268_90f2_a3bf_1bd830fd87c1_MD0008_00 The acid-base properties of organic compounds can be used to increase their separation during extraction. Compounds with acidic or basic functional groups can enter the aqueous layer as ionic salts, which are formed by deprotonation or protonation by a base or acid of varying strengths, respectively. Strong organic bases form ionic salts easily when weak acids are added to a mixture. On the other hand, weaker bases such as amines are only protonated by strong acids. Likewise, carboxylic acids, which are considered relatively strong organic acids, can be deprotonated by strong and weak bases. However, phenols are much weaker acids that require strong bases to be deprotonated. For phosphatidylethanolamine and 2,6-dimethoxyphenol to enter the aqueous layer consecutively, their ionic salts must be formed in sequence. Phosphatidylethanolamine contains an amine group that can be protonated to form a water-soluble ammonium salt; therefore, a strong acid such as H₂SO₄ or HCl should be added to protonate the amino group. In contrast, 2,6-dimethoxyphenol has a weakly acidic hydroxyl group on the benzene ring that must be deprotonated to form an ionic salt. Only strong bases such as NaOH or KOH are able to remove protons from phenols. Consequently, the correct sequence of extraction steps would involve the addition of a strong acid followed by a strong base. (Choice A) The order in which phosphatidylethanolamine and 2,6-dimethoxyphenol enter the aqueous layer is reversed. (Choice B) The aqueous layer will contain only phosphatidylethanolamine. NaHCO₃(aq) is a weak base that cannot deprotonate 2,6-dimethoxyphenol. (Choice C) Neither phosphatidylethanolamine nor 2,6-dimethoxyphenol will enter the aqueous layer. Amines cannot be protonated by weak acids such as H₂CO₃(aq), and NaHCO₃ is a weak base that will not deprotonate phenols. Educational objective: Organic compounds with acidic or basic functional groups enter the aqueous layer as ionic salts when acids and bases are added to an extraction. Amines are weak bases that require strong acids to be protonated. Phenols are weak acids that are only deprotonated by strong bases.

Passage Two Key Ingredients Found in Many Soaps Are PEG 150