Passage
Ethanol is an important source of energy that is frequently used as a supplement to gasoline. It can be obtained from renewable resources such as the cellulose found in plant matter. When subjected to a process called gasification, the plant mass is converted to a mixture called syngas, composed predominantly of carbon monoxide and molecular hydrogen. Syngas can be passed over a rhodium catalyst to generate ethanol and other products. After using this method, a group of researchers analyzed the resulting products by gas chromatography using helium as a carrier gas. The results are shown in Figure 1.
Figure 1 Gas chromatograph of syngas catalysis productsMass spectrometry revealed that the process yielded similar amounts of ethanol, acetic acid, and acetaldehyde, with trace amounts of ethane. In addition, the ethanol peak was found to be contaminated with ethyl acetate. Another group of researchers in the same laboratory had recently produced Compound 1 as a by-product in a separate reaction. They combined Compound 1 with purified ethyl acetate to form megestrol acetate, a drug used in the treatment of certain cancers. This reaction also produced ethanol, as shown in Scheme 1.
Scheme 1
Adapted from Lopez L, Velasco J, Montes V, Marinas A, Cabrera S, Boutonnet M, Järås S. Catalysts 2015.
-The conversion of megestrol to megestrol acetate shown in Scheme 1 represents which kind of reaction?

Question

Passage
Ethanol is an important source of energy that is frequently used as a supplement to gasoline. It can be obtained from renewable resources such as the cellulose found in plant matter. When subjected to a process called gasification, the plant mass is converted to a mixture called syngas, composed predominantly of carbon monoxide and molecular hydrogen. Syngas can be passed over a rhodium catalyst to generate ethanol and other products. After using this method, a group of researchers analyzed the resulting products by gas chromatography using helium as a carrier gas. The results are shown in Figure 1.

Figure 1 Gas chromatograph of syngas catalysis productsMass spectrometry revealed that the process yielded similar amounts of ethanol, acetic acid, and acetaldehyde, with trace amounts of ethane. In addition, the ethanol peak was found to be contaminated with ethyl acetate. Another group of researchers in the same laboratory had recently produced Compound 1 as a by-product in a separate reaction. They combined Compound 1 with purified ethyl acetate to form megestrol acetate, a drug used in the treatment of certain cancers. This reaction also produced ethanol, as shown in Scheme 1.

Scheme 1
Adapted from Lopez L, Velasco J, Montes V, Marinas A, Cabrera S, Boutonnet M, Järås S. Catalysts 2015.
-The conversion of megestrol to megestrol acetate shown in Scheme 1 represents which kind of reaction?

Quizplus · Accepted Answer

11ecba2d_126c_fdd8_a3bf_51bb73e402e1_MD0008_00 Transesterification is the reaction between an ester and an alcohol that results in an exchange of alkoxy and alcohol R groups. The reaction can be either acid-catalyzed or base-catalyzed, and involves nucleophilic attack by the alcohol on the carbonyl carbon of the ester to form a new alkoxy group. The original alkoxy group leaves and becomes protonated to form a new alcohol. The conversion of megestrol to megestrol acetate described in Scheme 1 is a reaction between an alcohol (megestrol) and an ester (ethyl acetate). It results in the formation of a bond between megestrol and acetate, and the ethoxy group leaves as ethanol. This is an example of transesterification. (Choice B) Saponification is the removal of an alkoxy group from an ester by a base. It forms a carboxylic acid and an alcohol rather than a new ester and an alcohol. (Choice C) An aldol condensation is a carbon-carbon bond forming reaction that requires two carbonyl compounds (ketones and/or aldehydes) rather than an ester and an alcohol. It forms an α,β-unsaturated carbonyl compound rather than an ester and an alcohol. (Choice D) Oxidation is the loss of electrons by an atom. In organic molecules, it generally results in fewer C-H bonds and more C-O bonds, neither of which occurs in the described process. Educational objective: Transesterification is the exchange of alcohol and alkoxy R groups between an ester and an alcohol.

Passage Ethanol Is an Important Source of Energy That Is Frequently