Chemical Identity and Physical Properties

Crotyl Chloride, systematically named 1-chloro-2-butene, is a four-carbon allylic chloride with the condensed formula C₄H₇Cl and a molecular weight of approximately 90.55 g/mol. The compound exists as two geometric isomers: the trans (E) isomer (CAS 591-97-9) and the cis (Z) isomer (CAS 625-67-2). Commercial reagent-grade material is predominantly the trans isomer, though mixtures are often encountered.

Key physical characteristics include a low boiling point (approximately 84 °C for the trans isomer at atmospheric pressure), high volatility, and a pungent, lachrymatory odor. The compound is a colorless to pale yellow flammable liquid that is poorly miscible with water but readily miscible with common organic solvents such as diethyl ether, dichloromethane, and tetrahydrofuran. Its allylic C–Cl bond is significantly more reactive toward substitution and elimination than a simple alkyl chloride due to resonance stabilization of the developing allylic cation or anion in transition states.

Reactivity and Synthetic Utility

The defining chemical feature of Crotyl Chloride is its allylic chloride functionality, which renders it an exceptionally versatile electrophile in organic synthesis. The compound participates in a broad range of transformations:

• Nucleophilic Substitution (SN2 and SN2'): Crotyl Chloride reacts with carbon, oxygen, nitrogen, and sulfur nucleophiles under mild conditions. The allylic system allows both direct displacement (SN2) and allylic transposition (SN2'), often yielding regioisomeric product mixtures whose ratios depend on the nucleophile, solvent, and temperature.
• Metal-Mediated Allylation: In the presence of metals such as zinc, indium, or chromium, Crotyl Chloride generates organometallic intermediates that add to aldehydes and ketones to afford homoallylic alcohols with defined stereochemistry. These reactions are foundational in the synthesis of polyketide natural products and other complex targets.
• Transition-Metal Catalysis: Crotyl Chloride serves as an allyl electrophile in palladium- and nickel-catalyzed cross-coupling reactions, enabling C–C bond formation with nucleophiles such as organozinc, organoboron, and malonate derivatives.
• Grignard and Organolithium Preparation: The compound can be converted to crotylmagnesium chloride or crotyllithium reagents, extending its utility to carbonyl addition chemistry.

The synthetic importance of crotylation reactions lies in the simultaneous generation of a new stereocenter and an alkene handle available for further functionalization, making Crotyl Chloride a valuable building block in multi-step total synthesis.

Safe Handling, Storage, and Hazard Information

Crotyl Chloride is classified as a flammable liquid and presents significant health and safety hazards that require strict laboratory controls. The following precautions are essential:

• Flammability: The compound has a low flash point and must be kept away from open flames, sparks, and hot surfaces. Use only in areas free of ignition sources.
• Lachrymator and Irritant: Vapor and liquid contact cause severe irritation to eyes, skin, and respiratory mucosa. Work exclusively in a well-functioning chemical fume hood. Wear chemical splash goggles, nitrile or neoprene gloves, and a lab coat as minimum PPE.
• Toxicity: Inhalation of vapors may cause respiratory tract irritation and central nervous system effects. Avoid prolonged or repeated exposure.
• Reactivity: Incompatible with strong oxidizing agents, strong bases, and moisture. The allylic chloride may slowly hydrolyze on prolonged exposure to atmospheric moisture.
• Storage: Store in a tightly sealed container in a cool (≤25 °C), dry, and well-ventilated area, segregated from oxidizers and flammable materials. Refrigerated storage under inert atmosphere is recommended to minimize isomerization and decomposition.
• Waste Disposal: Dispose of as halogenated organic solvent waste in accordance with local, national, and institutional regulations.

Always consult the current Safety Data Sheet (SDS) for Aladdin product C153477 before use.

Representative Laboratory Applications

Crotyl Chloride finds broad application across academic and industrial research settings. Some of the most important uses include:

• Homoallylic Alcohol Synthesis: Reaction of Crotyl Chloride with metals (Zn, In) in aqueous or organic media generates crotylmetal species that add to aldehydes to give branched homoallylic alcohols. The diastereoselectivity (syn vs. anti) is controlled by the geometry of the crotyl-metal intermediate and the reaction conditions, making this a key strategy in asymmetric synthesis.
• Natural Product Total Synthesis: Crotyl Chloride-derived intermediates appear in the synthesis of polyketides, terpenoids, and macrolides, where the installed alkene serves as a handle for olefin metathesis, epoxidation, dihydroxylation, or further functionalization.
• Polymer and Material Science: Crotyl-functionalized polymers can be accessed via allylation of polymer backbones using Crotyl Chloride, introducing pendant alkene groups for post-polymerization modification.
• Preparation of Allyl Ethers and Esters: O-Alkylation of alcohols and carboxylates with Crotyl Chloride under basic conditions provides crotyl ethers and esters, useful as protecting groups or masked homoallyl equivalents.
• Allylamine Synthesis: N-Alkylation of amines with Crotyl Chloride affords allylamines that are substrates for aza-Cope/Mannich and other cascade reactions.

Ordering Information and Product Specifications

Aladdin Scientific supplies Crotyl Chloride under SKU C153477. Researchers are encouraged to verify current purity specifications, available pack sizes, and certificate of analysis data on the Aladdin product page or by contacting technical support.

When ordering, consider the following:

• Quantity: Select pack size appropriate for projected consumption to minimize storage duration and degradation risk.
• Purity: Confirm that the stated purity and isomer composition meet the requirements of your synthetic protocol. GC or NMR analysis of the cis/trans isomer ratio may be relevant for stereoselective applications.
• Shipping: As a flammable liquid, Crotyl Chloride is subject to hazardous materials shipping regulations (e.g., IATA, DOT). Ground shipping within domestic regions is typically used. Contact Aladdin logistics for export inquiries.
• Regulatory Compliance: Confirm any local restrictions on the receipt and storage of allylic halides in your jurisdiction prior to ordering.

For technical questions about applications or compatibility, contact Aladdin's technical support team.