Understanding the fundamental chemistry of key intermediates is vital for successful synthesis. (S)-4-Chloro-3-hydroxybutyronitrile (CAS: 127913-44-4) is a prime example of a molecule whose specific structure and properties dictate its utility, particularly in pharmaceutical and fine chemical synthesis.

The chemical structure of (S)-4-Chloro-3-hydroxybutyronitrile is characterized by a four-carbon chain. At one end, there is a nitrile group (-CN), a versatile functional group that can undergo various transformations like hydrolysis to carboxylic acids or reduction to amines. Adjacent to the nitrile group, at the alpha-carbon, is a hydroxyl group (-OH), which can participate in esterification, etherification, or oxidation reactions. Crucially, the carbon atom bearing the hydroxyl group is a chiral center, designated as (S) in this specific isomer. This chirality is what makes it an invaluable building block for creating enantiomerically pure compounds, a requirement in many sophisticated chemical syntheses, especially for pharmaceuticals.

Physically, (S)-4-Chloro-3-hydroxybutyronitrile is typically described as a colorless to yellowish liquid. Its density is approximately 1.250 g/mL at 20°C, and its refractive index (n20/D) is around 1.474. These properties are important for characterization and quality control. The boiling point is noted at 110°C/1 mmHg, indicating it is a relatively low-volatility liquid under vacuum, which is common for many intermediates used in synthesis to avoid degradation at higher temperatures.

The synthesis of (S)-4-Chloro-3-hydroxybutyronitrile often involves asymmetric reduction of a precursor ketone or enzymatic transformation to introduce the specific (S) stereochemistry. For example, reduction of 4-chloro-3-oxobutyronitrile using stereoselective reducing agents or biocatalysts can yield the desired chiral alcohol. The introduction of the chlorine atom at the gamma-position and the nitrile group at the terminal position are also key steps in building the molecule. The precise synthetic route employed by manufacturers can influence purity, yield, and cost, making it a subject of ongoing research and process optimization.

Its stability under normal temperatures and pressures is a significant advantage, simplifying handling and storage. However, like many organic molecules, it may be sensitive to strong oxidizing agents and bases. Therefore, proper storage conditions, often in a cool, dry, well-ventilated area with the container kept closed, are recommended to maintain its integrity.

The combination of its functional groups and defined chirality makes (S)-4-Chloro-3-hydroxybutyronitrile a sought-after intermediate for complex organic synthesis. Its role as a precursor for atorvastatin and carbapenem antibiotics, among other applications, demonstrates the power of precisely engineered molecules in driving innovation in the pharmaceutical industry. Understanding its chemical nuances allows chemists to leverage its full potential in creating novel and effective compounds.