Preparation of arabinose from glucose

 The preparation of arabinose from glucose typically involves a series of chemical reactions, as glucose and arabinose are different monosaccharides. Arabinose is a pentose sugar (5-carbon sugar), whereas glucose is a hexose sugar (6-carbon sugar). There are various methods to prepare arabinose from glucose, including chemical oxidation, isomerization, and selective degradation. One of the most straightforward approaches is through the Ruff degradation process.

Steps for preparing arabinose from glucose via the Ruff degradation:

1. Oxidation of glucose to gluconic acid:

   • Glucose is first oxidized to gluconic acid using bromine water (Br₂ + H₂O) or nitric acid. This reaction converts the aldehyde group (–CHO) at C1 of glucose into a carboxyl group (–COOH), forming gluconic acid.
   $$\text{C₆H₁₂O₆ (Glucose)}+B{r}_2+H_{2}O\to \text{C₆H₁₂O₇ (Gluconic Acid)}+2HBr$$

2. Decarboxylation of gluconic acid to arabinose:

   • The next step involves the Ruff degradation, which is a sequential process involving:
     • The oxidation of gluconic acid to its corresponding aldonic acid (D-arabinonic acid).
     • Then, hydrogen peroxide (H₂O₂) and ferrous sulfate (FeSO₄) are added. This causes a decarboxylation reaction, removing the C1 carboxyl group, resulting in the formation of arabinose (a 5-carbon sugar).

$$\text{C₆H₁₂O₇ (Gluconic Acid)}\stackrel{\text{H₂O₂ + FeSO₄}}{\to }\text{C₅H₁₀O₅ (Arabinose)}+C{O}_2$$

Summary:

• Glucose (C6) → Gluconic Acid (C6) via oxidation.
• Gluconic Acid → Arabinose (C5) via Ruff degradation (decarboxylation).

This method, however, is not highly efficient for large-scale industrial processes, and nowadays, biochemical and enzymatic methods might also be used, depending on the desired purity and quantity of arabinose required.