Question

Which of the following sequences is known as a Kiliani-Fischer chain elongation? Group of answer choices 1. CH3OH, H+, Δ 2. AgNO3, Δ 1. CN- 2. H2, Pd/BaSO4 3. H3O+ 1. Fe3+, H2O2 2. Br2, H2O 3. Ca(OH)2 1. NaBH4 2. H2O 3. Br2, H2O 1. acetic anhydride (excess), pyridine 2. CH3I (excess), Ag2O

Answer 1

The Kiliani-Fischer chain elongation involves elongating the carbon chain of an aldose sugar using cyanide ions, followed by hydrolysis and other steps, but the sequences provided do not correspond directly to this method.

Step-by-step explanation:

The Kiliani-Fischer chain elongation refers to a method in carbohydrate chemistry that is used to lengthen the carbon chain of an aldose sugar. This is achieved through the use of cyanide ions (CN-) which add to the aldehyde group to form a cyanohydrin, followed by hydrolysis and further steps to complete the sugar chain elongation. None of the sequences listed correspond to the Kiliani-Fischer synthesis directly, as this process specifically involves cyanide addition to an aldose. However, if only the first step is considered (1. CN-), it could be loosely associated with the initial stage of Kiliani-Fischer synthesis, but lacks subsequent steps such as hydrolysis and reduction that are integral to the process.

Answer 2

The correct option is: 1. CN- 2. H₂, Pd/BaSO₄ 3. H3O+

Step-by-step explanation:

Kiliani-Fischer synthesis is a method used for the elongation of the carbon chain of an aldose sugar, by the addition of carbon to aldehyde end of the aldose sugar.

In this method, the aldose sugar is treated with HCN in the first step, followed by reduction with hydrogen (H₂) in the presence of palladium/ barium sulfate (Pd/BaSO₄) as catalyst in second step and then hydrolyzed in third step, to give a mixture of two elongated diastereomeric aldose sugars, called epimers.