Both NaBH₄ and NaBD₄ are commercially available, and D₂O is common and inexpensive. Show how you would synthesize the following labeled compounds, starting with butan-2-one.
(a)

Verified step by step guidance

1. Step 1: Begin with butan-2-one (CH3COCH2CH3), which is a ketone. The goal is to reduce the ketone group to an alcohol group while introducing a deuterium (D) atom.
2. Step 2: Use NaBD4 (sodium borodeuteride) as the reducing agent. NaBD4 is specifically used to introduce deuterium during the reduction process. The hydride (H-) in NaBH4 is replaced with deuteride (D-), allowing the deuterium to be incorporated into the molecule.
3. Step 3: Perform the reduction reaction. The NaBD4 will donate a deuterium atom to the carbonyl carbon of butan-2-one, converting the C=O bond into a C-D bond and forming a secondary alcohol.
4. Step 4: After the reduction, the product will be labeled as CH3CH(OD)CH2CH3. To ensure the hydroxyl group (-OH) is not exchanged with hydrogen, the reaction should be carried out in D2O (deuterium oxide) as the solvent.
5. Step 5: The final labeled compound is CH3CH(OH)CH2CH3, where the deuterium atom is attached to the carbon that was originally part of the carbonyl group in butan-2-one.

Key Concepts

Reduction Reactions

Reduction reactions involve the gain of electrons or hydrogen, or the loss of oxygen. In organic chemistry, reducing agents like NaBH4 (sodium borohydride) are commonly used to convert carbonyl compounds, such as ketones and aldehydes, into alcohols. Understanding how these reactions work is crucial for synthesizing compounds from starting materials like butan-2-one.

Deuteration

Deuteration is the process of replacing hydrogen atoms in a molecule with deuterium, a heavier isotope of hydrogen. This is significant in organic synthesis when using NaBD4, which introduces deuterium into the product. Recognizing how deuteration affects molecular structure and properties is essential for synthesizing labeled compounds.

NMR Spectroscopy

Nuclear Magnetic Resonance (NMR) spectroscopy is a powerful analytical technique used to determine the structure of organic compounds. It provides information about the number and environment of hydrogen atoms in a molecule. Understanding NMR is important for analyzing the products of the synthesis and confirming the incorporation of deuterium in the labeled compounds.