(+)-alpha-Pinene: Properties, Safety & Lab Use Guide
(+)-alpha-Pinene: Properties, Safety & Lab Use Guide
(+)-alpha-Pinene is a chiral, naturally occurring bicyclic monoterpene widely used in chemical synthesis, biological research, and flavor and fragrance studies, serving as both a valuable building block and a reference standard in laboratory investigations.
- CAS Number
- 7785-70-8
- Molecular Formula
- C₁₀H₁₆
- Molecular Weight
- 136.23 g/mol
- Optical Rotation
- (+) dextrorotatory (positive optical rotation)
- Appearance
- Colorless to pale yellow liquid with a characteristic pine-like odor
- Chemical Class
- Bicyclic monoterpene
- Primary Source
- Conifer essential oils, particularly pine resin (turpentine)
Physicochemical Properties of (+)-alpha-Pinene
(+)-alpha-Pinene (CAS 7785-70-8) is the dextrorotatory enantiomer of alpha-pinene, a bicyclic monoterpene with the molecular formula C₁₀H₁₆ and a molecular weight of 136.23 g/mol. It features a strained four-membered ring fused to a six-membered ring, conferring high reactivity in ring-opening and cycloaddition reactions.
Key physicochemical parameters include a boiling point of approximately 155–156 °C at atmospheric pressure, a density of approximately 0.858 g/mL at 25 °C, and a refractive index of approximately 1.464. The compound is practically insoluble in water but miscible with most common organic solvents including ethanol, diethyl ether, chloroform, and hexane. Its vapor pressure is moderate, contributing to its characteristic and readily detectable pine-like odor even at room temperature.
The positive optical rotation distinguishes (+)-alpha-pinene from its (−)-enantiomer and from the structurally related beta-pinene. Enantiomeric purity should be verified by polarimetry when stereochemical fidelity is critical to the experiment.
Safe Handling and Storage Guidelines
(+)-alpha-Pinene is a flammable liquid and should be handled with appropriate precautions. Its flash point is approximately 33 °C, classifying it as a flammable liquid (GHS category). Always work in a well-ventilated fume hood when handling bulk quantities or during prolonged exposure, as vapor inhalation may cause respiratory irritation, headache, or dizziness.
Personal protective equipment (PPE) requirements include chemical-resistant gloves (nitrile or neoprene recommended), safety goggles, and a lab coat. Avoid contact with skin and eyes; in case of contact, flush thoroughly with water for at least 15 minutes and seek medical attention if irritation persists. Do not allow the compound to drain into water courses or sewage systems, as it may be harmful to aquatic organisms.
For storage, keep the reagent in a tightly sealed amber glass container away from heat, sparks, and open flames. Store in a cool, dry, well-ventilated area at 2–8 °C or as specified on the product label, away from oxidizing agents and strong acids. Under appropriate storage conditions, the reagent is stable; however, alpha-pinene is susceptible to autoxidation upon prolonged exposure to air and light, forming potentially sensitizing peroxide species. Periodically verify purity by GC if the container has been opened multiple times or stored for extended periods.
Laboratory Applications and Research Uses
(+)-alpha-Pinene serves as a versatile reagent and starting material across multiple research disciplines. In synthetic organic chemistry, it is widely employed as a chiral building block for the preparation of enantiomerically enriched terpenoid natural products, pharmaceutical intermediates, and chiral auxiliaries. Its strained bicyclic framework facilitates stereoselective ring-opening reactions, hydroboration, and solvolysis studies.
In chemical biology and pharmacology, (+)-alpha-pinene has been investigated for its biological activities, including reported anti-inflammatory, antimicrobial, and bronchodilatory effects, making it a useful reference compound and positive control in cell-based assays and in vitro bioactivity screens. It is also employed as a standard in analytical chemistry, particularly in the qualitative and quantitative analysis of essential oils, food flavors, and environmental air samples by GC and GC-MS.
In materials science, alpha-pinene serves as a renewable biosourced feedstock for the synthesis of terpene-derived polymers, resins, and adhesives. Researchers working on green chemistry and sustainable materials frequently employ it as a bio-based monomer. Aladdin Scientific offers (+)-alpha-Pinene (SKU: P1456614) suitable for these research purposes.
Quality Considerations and Analytical Verification
For research applications where stereochemical purity is critical, the optical rotation of the (+)-alpha-pinene lot should be confirmed upon receipt. The expected specific rotation [α]D²⁰ for the (+)-enantiomer is positive; consult the certificate of analysis (CoA) supplied with each lot for the measured value.
Gas chromatography (GC) is the primary method for assessing chemical purity. A high-purity reagent should show a dominant single peak corresponding to alpha-pinene, with minimal peaks attributable to beta-pinene, camphene, limonene, or oxidized impurities such as myrtenol or pinocarvone. If GC purity falls below specification after prolonged storage, do not use the reagent for sensitive bioassays or enantioselective synthesis without re-purification.
When using (+)-alpha-pinene as a GC or GC-MS reference standard, verify retention time and mass spectral fragmentation pattern against authenticated reference spectra. Key diagnostic ions in EI-MS include m/z 136 (M⁺), 121, 93, and 77. Retention indices on standard non-polar columns (e.g., DB-1 or equivalent) are well-documented in the literature and should be used as an orthogonal confirmation of identity.
Waste Disposal and Environmental Considerations
Spent (+)-alpha-Pinene and contaminated materials must be disposed of in accordance with local, national, and institutional regulations governing flammable organic solvents and chemical waste. Do not pour down the drain or into the environment. Collect waste in clearly labeled, solvent-compatible containers designated for halogen-free organic waste, and arrange for collection by a licensed chemical waste contractor.
Although (+)-alpha-pinene is a naturally occurring compound found abundantly in the environment, concentrated laboratory waste should still be treated as hazardous due to its flammability and potential ecotoxicity at high local concentrations. Researchers should consult their institution's Environmental Health and Safety (EHS) office for site-specific disposal requirements.
Spills should be contained immediately using inert absorbent materials (e.g., vermiculite, dry sand) and collected into appropriate waste containers. Avoid using sawdust or other combustible absorbents. Ensure adequate ventilation during cleanup operations to prevent vapor accumulation above the lower explosive limit (LEL).
Frequently asked questions
What is the difference between (+)-alpha-Pinene and (-)-alpha-Pinene?
(+)-alpha-Pinene and (−)-alpha-Pinene are enantiomers sharing identical molecular formula, molecular weight, and most physicochemical properties, but differing in the direction of optical rotation and their interactions with chiral environments. The (+)-form is dextrorotatory and predominates in many conifer species of the Northern Hemisphere, whereas the (−)-form is levorotatory. In stereoselective synthesis and chiral biological assays, the two enantiomers may produce distinct outcomes and must not be used interchangeably.
How should I prevent (+)-alpha-Pinene from degrading during storage?
To minimize autoxidation, store (+)-alpha-Pinene under an inert atmosphere (nitrogen or argon) in a tightly sealed amber glass container at 2–8 °C, protected from light. Avoid repeated freeze-thaw cycles and minimize headspace in the container. If the reagent will be used intermittently over a long period, consider aliquoting into smaller vials to reduce cumulative air exposure. Periodically monitor purity by GC to detect early-stage oxidative degradation.
Is (+)-alpha-Pinene suitable for use as a GC-MS reference standard for essential oil analysis?
Yes, (+)-alpha-Pinene is commonly used as a reference standard in GC and GC-MS analysis of essential oils, terpene mixtures, and food or environmental samples. Confirm the purity and optical rotation from the certificate of analysis before use. Verify identity by matching the retention index on a standardized column and the EI-MS fragmentation pattern (key ions: m/z 136, 121, 93, 77) against authenticated reference data.
Can (+)-alpha-Pinene be used in cell-based biological assays?
(+)-alpha-Pinene has been employed in in vitro biological studies investigating anti-inflammatory and antimicrobial activities. When preparing working solutions for cell-based assays, note that the compound has very low water solubility; use a minimal volume of a biocompatible solvent such as DMSO or ethanol to prepare a concentrated stock, then dilute into aqueous cell culture medium. Always include appropriate solvent vehicle controls, and keep the final solvent concentration below cytotoxic thresholds (typically ≤0.1% DMSO).
What purity grade of (+)-alpha-Pinene should I select for enantioselective synthesis?
For enantioselective synthesis where chirality transfer is essential, select the highest available enantiomeric excess (ee) grade. Review the certificate of analysis for both chemical purity (GC %) and optical rotation ([α]D), and confirm these meet your experimental requirements. Using a lower-ee material can lead to diminished stereocontrol and product ee, potentially compromising the scientific validity of the synthesis.
References
- Bakkali, F. et al. Biological effects of essential oils – a review. Food and Chemical Toxicology, 2008.
- Corey, E.J. & Ensley, H.E. Preparation of an optically active prostaglandin intermediate via asymmetric induction. Use of (+)-alpha-pinene-derived chiral auxiliary. Journal of the American Chemical Society, 1975.
- Adams, R.P. Identification of Essential Oil Components by Gas Chromatography/Mass Spectrometry. Allured Publishing Corporation, 4th ed.
- Ruzicka, L. The isoprene rule and the biogenesis of terpenic compounds. Experientia, 1953.
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