2-Chloro-1,1,1-trimethoxyethane: Properties, Synthesis & Lab Uses

2-Chloro-1,1,1-trimethoxyethane is a bifunctional organic reagent combining a reactive chloromethyl group with a trimethyl orthoester moiety, making it a versatile building block for organic synthesis and functional-group manipulation.

IUPAC Name

2-Chloro-1,1,1-trimethoxyethane

Common Synonym

Chloroacetaldehyde trimethyl acetal

Molecular Formula

C5H11ClO3

Molecular Weight

154.59 g/mol

Key Functional Groups

Alkyl chloride, orthoester (trimethoxy)

Primary Use

Electrophilic building block in organic synthesis

Physical State

Colorless to pale yellow liquid

SKU

D304550

Chemical Identity and Physical Properties

2-Chloro-1,1,1-trimethoxyethane, also known as chloroacetaldehyde trimethyl acetal, has the molecular formula C₅H₁₁ClO₃ and a molecular weight of approximately 154.59 g/mol. The compound features two distinct reactive sites: a primary alkyl chloride at the C-2 position and a trimethyl orthoester at the C-1 position. This combination of electrophilic and masked-carbonyl functionality within a single, relatively small molecule is the basis for its synthetic utility.

Under standard conditions the compound presents as a colorless to pale yellow liquid with a characteristic ethereal odor. It should be stored in a cool, dry, well-ventilated location, away from moisture and strong bases, which can promote hydrolysis of the orthoester moiety. Compatibility considerations include sensitivity to protic solvents under acidic conditions, which release the parent aldehyde chloroacetaldehyde upon acetal hydrolysis.

Synthesis and Preparation

The most well-established route to 2-Chloro-1,1,1-trimethoxyethane is the trimethyl orthoformate-based protection of chloroacetaldehyde, or equivalently, the reaction of chloroacetaldehyde with trimethyl orthoformate under acid catalysis. In practice, chloroacetaldehyde reacts with trimethyl orthoformate (or alternatively excess methanol) under anhydrous acidic conditions to afford the stable acetal. The reaction proceeds via oxocarbenium-ion intermediates typical of acetal-forming reactions, with methanol generated as a by-product that must be removed to drive the equilibrium toward product.

Alternative preparations involve direct halogenation of 1,1,1-trimethoxyethane; however, control of regioselectivity can be challenging and the chloroacetaldehyde-acetal route generally affords higher purity product. For research-grade reagent supply, the compound is available directly from Aladdin Scientific (SKU D304550), eliminating the need for in-house preparation in most laboratory settings.

Laboratory Applications in Organic Synthesis

The bifunctional nature of 2-Chloro-1,1,1-trimethoxyethane makes it a valuable electrophilic synthon. The primary alkyl chloride is an active electrophile amenable to S_N2 reactions with a broad range of nucleophiles—including amines, thiols, alcohols, azides, phosphines, and stabilized carbanions—enabling efficient C–N, C–S, C–O, C–P, and C–C bond formation.

The orthoester group simultaneously serves as a protected form of a carboxylate equivalent. Under mild aqueous acid conditions, the trimethyl orthoester hydrolyzes to give first a dimethyl acetal and ultimately the free aldehyde (or, with further oxidation, a carboxylic acid derivative). This two-stage unmasking provides synthetic flexibility: the alkyl chloride can be used in a coupling step first, and the orthoester can subsequently be revealed as an aldehyde for further elaboration—e.g., reductive amination, Wittig olefination, or aldol condensation.

Reported applications include the synthesis of heterocyclic frameworks (e.g., oxazoles, thiazolines, imidazoles) where the chloro and masked-aldehyde functions participate sequentially, as well as use as a two-carbon homologation unit in the assembly of amino acid analogs and pharmaceutical intermediates. It is also employed as a versatile linker reagent in solid-phase synthesis contexts where orthogonal deprotection is required.

Handling, Safety, and Storage Guidelines

As with all alkyl halide reagents, 2-Chloro-1,1,1-trimethoxyethane should be handled with appropriate personal protective equipment, including chemical-resistant gloves, safety eyewear, and a laboratory coat. Operations involving this compound should be conducted in a well-ventilated fume hood to minimize inhalation exposure to vapors. The compound is a lachrymator precursor; hydrolysis to chloroacetaldehyde, a known lachrymator and mutagen, underscores the importance of preventing contact with aqueous or protic environments during use.

For storage, the reagent should be kept in a tightly sealed container under an inert atmosphere (nitrogen or argon) at 2–8 °C or as specified on the product label. Prolonged exposure to air, moisture, or light should be avoided. Incompatible materials include strong bases, strong oxidizing agents, and water. Waste disposal must comply with local and institutional regulations governing halogenated organic solvents and reactive chemicals.

Researchers should consult the current Safety Data Sheet (SDS) provided by Aladdin Scientific (SKU D304550) for the most up-to-date hazard classifications, first-aid measures, and regulatory information before working with this compound.

Frequently asked questions

What is the difference between 2-Chloro-1,1,1-trimethoxyethane and chloroacetaldehyde?

Chloroacetaldehyde is the free aldehyde form, which is highly reactive, lachrymatory, and difficult to handle and store. 2-Chloro-1,1,1-trimethoxyethane is the corresponding trimethyl acetal (orthoester) form, in which the aldehyde carbonyl is masked as a stable orthoester. This protection renders the compound significantly easier to handle while the aldehyde can be released on demand by mild acid hydrolysis.

Under what conditions does the orthoester group hydrolyze?

The trimethyl orthoester in 2-Chloro-1,1,1-trimethoxyethane hydrolyzes readily under mild aqueous acidic conditions (e.g., dilute HCl or p-TsOH in aqueous acetone or THF), first to the dimethyl acetal and then to the free aldehyde. The hydrolysis is much slower under neutral or basic aqueous conditions, and essentially does not occur in anhydrous aprotic solvents, allowing selective manipulation of the alkyl chloride under appropriate conditions.

What nucleophiles are compatible with the alkyl chloride of this compound?

The primary alkyl chloride of 2-Chloro-1,1,1-trimethoxyethane is reactive toward a wide range of nucleophiles including primary and secondary amines, thiols, alkoxides, azides, phosphines, and soft carbon nucleophiles such as enolates and organometallic species. Reactions are typically performed in polar aprotic solvents (DMF, acetonitrile, DMSO) with a suitable base to neutralize the HCl generated, taking care to maintain anhydrous conditions to preserve the orthoester integrity.

How should I store 2-Chloro-1,1,1-trimethoxyethane to maximize shelf life?

Store the compound in a tightly sealed container under an inert atmosphere (nitrogen or argon) at 2–8 °C, protected from light and moisture. Avoid repeated freeze-thaw cycles. Always consult the current SDS (Aladdin Scientific, SKU D304550) and product label for specific storage recommendations.

Is 2-Chloro-1,1,1-trimethoxyethane available in multiple grades or pack sizes?

Aladdin Scientific offers 2-Chloro-1,1,1-trimethoxyethane under SKU D304550. For information on available purity grades, pack sizes, and current pricing, please visit the product page on the Aladdin Scientific website or contact our customer service team.

References

1. March, J. Advanced Organic Chemistry: Reactions, Mechanisms, and Structure, 4th ed.; Wiley-Interscience: New York, 1992. (General acetal and orthoester chemistry)
2. Clayden, J.; Greeves, N.; Warren, S. Organic Chemistry, 2nd ed.; Oxford University Press: Oxford, 2012. (Protecting group strategies for aldehydes and orthoesters)
3. Aladdin Scientific. Product Page: 2-Chloro-1,1,1-trimethoxyethane, SKU D304550. Aladdin Scientific, Shanghai.

Products are supplied for research and development use only. Not for use in humans, animals, diagnosis, or therapy.