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

-Compound E does not give a positive result for the Lucas test. However, after reaction with LiAlH₄, a positive result for the Lucas test is observed. Which compound is the product of the reaction of Compound E with LiAlH₄?

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

-Compound E does not give a positive result for the Lucas test. However, after reaction with LiAlH₄, a positive result for the Lucas test is observed. Which compound is the product of the reaction of Compound E with LiAlH₄?

Quizplus · Accepted Answer

11ecba2d_1291_2741_a3bf_3b4b0e059a4e_MD0008_00 Reduction of a carbonyl (C=O) decreases its oxidation state, decreases the number of C-O bonds, and increases the number of C-H bonds, yielding an alcohol. The metal hydride LiAlH₄ is a reducing agent and contains four hydride ions (H:⁻). The hydride ion acts as a nucleophile and attacks the electrophilic carbonyl carbon, forming a new C-H bond and decreasing the number of C-O bonds (a reduction). In this manner, aldehydes and ketones are reduced to primary (1°) and secondary (2°) alcohols, respectively. Accordingly, if Compound E (a ketone) is reacted with LiAlH₄, Compound E will be reduced to a secondary alcohol, which gives a positive result for the Lucas test. Compounds are named based on the number of carbons in the longest continuous carbon chain (prefix) and the highest-priority functional group (suffix). The carbons are numbered to give the highest-priority functional group the smallest number, which is added to the beginning of the parent chain name. Applying the nomenclature rules, Compound E is a four-carbon (prefix but-) ketone (suffix -one) with the name 2-butanone. The name of the 2° alcohol formed from the reduction of 2-butanone is obtained by changing the ketone suffix -one to the alcohol suffix -ol to give butanol. The hydroxyl group for this compound is on carbon 2, so the name of the 2° alcohol product is 2-butanol. (Choices A and B) Reduction of a ketone results in a 2° alcohol rather than an aldehyde or a 1° alcohol. (Choice D) Compound E is 2-butanone. Because it is what reacts with LiAlH₄, it cannot be the product of the reaction. Educational objective: Reduction of an aldehyde or ketone with a reducing agent, such as LiAlH₄, reduces the number of C-O bonds and increases the number of C-H bonds to form a 1° and 2° alcohol, respectively. Ketones are named using the suffix -one; alcohols are named using the suffix -ol.

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