Passage
Students used three classification tests to study the reactivity of alcohol, aldehyde, and ketone functional groups in organic compounds. The organic compounds provided to the students are given in Table 1.Table 1 Organic Compounds Tested
First, the students performed the Lucas test by mixing a few drops of each compound with 2 mL of the Lucas reagent (ZnCl₂ and HCl) . This reagent is used to test for secondary and tertiary alcohols. A positive test result is indicated by a cloudy reaction mixture upon addition of the Lucas reagent due to the formation of an insoluble compound by an S_N1 reaction with a secondary or tertiary alcohol (Reaction 1) .
Reaction 1Next, a test for alcohols and aldehydes was performed by the addition of a drop of chromic acid reagent (CrO₃ dissolved in aqueous H₂SO₄) into samples of the organic compounds. The disappearance of the orange color from chromic acid and formation of a blue-green suspension is indicative of a positive result for this test. Compound A was found to be an example of a positive result, as shown in Reaction 2.
Reaction 2Finally, samples of the compounds were also dissolved in water, followed by the addition of NaOH and iodine. This test is known as the iodoform test, which is used to identify methyl ketones and secondary alcohols. A positive result is indicated by the formation of iodoform (CHI₃) , a yellow precipitate (Reaction 3) .
3Table 2 Selected Observations from the Classification Tests

-If the chromic acid reagent is added to Compound C, no reaction occurs because:

Question

Passage
Students used three classification tests to study the reactivity of alcohol, aldehyde, and ketone functional groups in organic compounds. The organic compounds provided to the students are given in Table 1.Table 1 Organic Compounds Tested

First, the students performed the Lucas test by mixing a few drops of each compound with 2 mL of the Lucas reagent (ZnCl₂ and HCl) . This reagent is used to test for secondary and tertiary alcohols. A positive test result is indicated by a cloudy reaction mixture upon addition of the Lucas reagent due to the formation of an insoluble compound by an S_N1 reaction with a secondary or tertiary alcohol (Reaction 1) .

Reaction 1Next, a test for alcohols and aldehydes was performed by the addition of a drop of chromic acid reagent (CrO₃ dissolved in aqueous H₂SO₄) into samples of the organic compounds. The disappearance of the orange color from chromic acid and formation of a blue-green suspension is indicative of a positive result for this test. Compound A was found to be an example of a positive result, as shown in Reaction 2.

Reaction 2Finally, samples of the compounds were also dissolved in water, followed by the addition of NaOH and iodine. This test is known as the iodoform test, which is used to identify methyl ketones and secondary alcohols. A positive result is indicated by the formation of iodoform (CHI₃) , a yellow precipitate (Reaction 3) .

3Table 2 Selected Observations from the Classification Tests

-If the chromic acid reagent is added to Compound C, no reaction occurs because:

Quizplus · Accepted Answer

11ecba2d_1290_15cb_a3bf_b1003135ce32_MD0008_00 Oxidation of an organic molecule requires a decrease in the number of C-H bonds and an increase in the number of C-O bonds. Primary and secondary alcohols can be oxidized to form aldehydes and ketones, respectively, using various oxidizing agents such as chromic acid. However, the tertiary carbon of a tertiary alcohol does not have any C-H bonds to lose; therefore, its number of bonds to oxygen cannot be increased. If the number of bonds to oxygen were increased without losing a bond to hydrogen, the carbon atom would have five bonds exceeding the maximum number possible (four bonds). The passage indicates that a secondary alcohol gives a positive result for the chromic acid test and that it is converted into a ketone in the process. As a result, an increase in the number of C-O bonds is achieved in the reaction indicating that the chromic acid test is an oxidation. Because (CH₃)₃COH (Compound C) is a tertiary alcohol, it cannot be oxidized. (Choice A) A tertiary alcohol can be reduced to a hydrocarbon; however, the chromic acid test is an oxidation rather than a reduction. (Choices C and D) An aldehyde can be both oxidized and reduced, but Compound C is an alcohol rather than an aldehyde. Educational objective: Oxidation of an organic molecule requires a decrease in the number of C-H bonds and an increase in the number of C-O bonds. Primary and secondary alcohols can be oxidized to aldehydes and ketones, respectively, by various oxidizing agents. Tertiary alcohols cannot be oxidized because the tertiary carbon does not have any C-H bonds to lose.

Passage Students Used Three Classification Tests to Study the Reactivity of of Alcohol