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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.
-According to Experiment 2, the samples from the lipid extract were diluted by what factor to generate the NMR samples?

Question

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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.
-According to Experiment 2, the samples from the lipid extract were diluted by what factor to generate the NMR samples?

Quizplus · Accepted Answer

11ecba2d_1269_a264_a3bf_fbacc9d8eca3_MD0008_00 Concentrated stock solutions or extracts usually require multistep dilutions because the desired amount of solute is too small to be transferred or measured accurately by laboratory instruments. In a simple dilution, the concentration of a stock solution is reduced by dissolving a small volume into a larger volume of solvent. A dilution factor (DF) is the magnitude by which the stock solution concentration is reduced. The dilution factor is calculated by dividing the volume of solute transferred V_T by the final volume of the solution V_F. In Experiment 2, the concentration of the organic layer was reduced by a two-step dilution to generate an NMR sample. In the first step, 0.5 mL (V_T1) of the lipid stock solution (organic layer) was dissolved in 9.5 mL (V_S₁) of solvent to produce a standard solution (V_F₁ = 10 mL). In the second step, 0.5 mL (V_T2) of the standard solution was dissolved in 0.5 mL (V_S2) of solvent for the NMR sample (V_F2 = 1.0 mL). The DF in this multistep dilution is calculated using the equation 11ecba2d_1269_c975_a3bf_619724d6c78c_MD0008_00 Substituting values for the transfer volumes (V_T1 and V_T2) and final volumes (V_F1 and V_F2) yields 11ecba2d_1269_c976_a3bf_b7cae402dbba_MD0008_00 11ecba2d_1269_c977_a3bf_85389aabbcc3_MD0008_00 Therefore, the lipid extract was diluted by a factor of 40. (Choice A) This value is the DF of the second step. (Choice B) This value is the DF of the first step. (Choice D) This value is based on an incorrect DF of the second step, 4 (which comes from using a V_F of 2.0 mL instead of 1.0 mL), and then multiplying by the correct DF of the first step, 20. Educational objective: Dilutions reduce the concentration of a solute by transferring a small volume of solute V_T into a larger volume of solvent V_S. The dilution factor is calculated by dividing V_T from the stock solution or the previous diluted solution by the final volume of the solution V_F.

Passage Two Key Ingredients Found in Many Soaps Are PEG 150