We have seen earlier that both aldoses and ketoses can be oxidized by a variety of methods, such as Tollens’ reagent, Fehling’s solution, and bromine water, to form aldonic acids. For example, glucose is oxidized at the aldehyde group to … Read more
Oxidation of Aldehydes with Tollens’ Reagent Tollens’ reagent is a mild oxidizing agent used for converting aldehydes to carboxylic acids. It is prepared from silver(I) oxide in aqueous ammonia and is commonly written as Ag₂O, NH₃, ⁻OH or Ag2O, NH4OH: … Read more
In this review, we will try to summarize what topics and types of questions from organic chemistry are covered in the MCAT test. Organic chemistry is tested as part of the Biological and Biochemical Foundations of Living Systems Section. You … Read more
The Wohl degradation cleaves the C1 – C2 bond of an aldose chain and shortens it by one carbon. Like in the Kiliani–Fischer synthesis, the transformation relies on first converting the aldehyde group to a cyanohydrin. Notice, however, … Read more
The Kiliani–Fischer synthesis lengthens the carbon chain of carbohydrates by adding one carbon to the aldehyde group of an aldose. For example, using this method, D-arabinose can be converted into a mixture of D-glucose and D-mannose: Notice that … Read more
The carbonyl group in aldoses and ketoses can be reduced by NaBH4 to a 1o and 2o alcohol, respectively. The product of this reaction is a polyalcohol called an alditol. The reduction of the ketones creates a new … Read more
Aldoses contain alcohol and aldehyde functional groups, which can be oxidized to carboxylic acids. Depending on the oxidizing agent, we can either selectively oxidize the aldehyde or involve the primary alcohol as well. If both groups are oxidized to a … Read more
Let’s see how the ether and ester derivatives of carbohydrates are prepared and used in organic synthesis. We have seen that carbohydrates undergo different epimerization and isomerization reactions in basic aqueous solutions and are therefore not stored under basic conditions. … Read more
Aldoses and ketoses undergo epimerization and other isomerization in basic solutions through keto-enol tautomerization. For example, a solution of D-glucose was found to establish an equilibrium containing both D-glucose and D-mannose: This type of reaction, characteristic of monosaccharides, … Read more
In the previous post, we mentioned that carbohydrates exist mainly in their cyclic forms when 5- or 6-membered rings are possible. Remember also that cyclic carbohydrates are hemiacetals which can be further transformed into acetals. The acetals of monosaccharides are … Read more
