Chloromethyltrimethylsilane
[CAS 2344-80-1]

Identification

• Classification: Chemical reagent >> Organic reagent >> Silane
• Name: Chloromethyltrimethylsilane
• Molecular Formula: C₄H₁₁ClSi
• Molecular Weight: 122.67
• CAS Registry Number: 2344-80-1
• EC Number: 219-058-5
• SMILES: C[Si](C)(C)CCl

Properties

• Density: 0.9±0.1 g/cm³ Calc.^*, 0.884 g/mL (Expl.)
• Melting point: 98 - 99 °C (Expl.), 98 - 99 °C (Expl.)
• Boiling point: 96.0±13.0 °C 760 mmHg (Calc.)^*
• Flash point: -2.8 °C (Calc.)^*, -2 °C (Expl.)
• Solubility: water insoluble (Expl.)
• Index of refraction: 1.397 (Calc.)^*, 1.418 (Expl.)

^* Calculated using Advanced Chemistry Development (ACD/Labs) Software.

Safety Data

• Hazard Symbols: GHS02;GHS07;GHS09 DangerGHS02
• Risk Statements: H225-H315-H319-H335-H411
• Safety Statements: P210-P233-P240-P241-P242-P243-P261-P264-P264+P265-P271-P273-P280-P302+P352-P303+P361+P353-P304+P340-P305+P351+P338-P319-P321-P332+P317-P337+P317-P362+P364-P370+P378-P391-P403+P233-P403+P235-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Flammable liquids	Flam. Liq.	2	H225
Specific target organ toxicity - single exposure	STOT SE	3	H335
Skin irritation	Skin Irrit.	2	H315
Eye irritation	Eye Irrit.	2	H319
Chronic hazardous to the aquatic environment	Aquatic Chronic	2	H411
Acute hazardous to the aquatic environment	Aquatic Acute	2	H401
Skin corrosion	Skin Corr.	1B	H314
Acute toxicity	Acute Tox.	4	H302
Serious eye damage	Eye Dam.	1	H318
Acute toxicity	Acute Tox.	4	H312
Acute toxicity	Acute Tox.	4	H332

• Transport Information: UN 1993

chemBlink Chemical Story

Chloromethyltrimethylsilane looks almost too simple to deserve special attention: a trimethylsilyl group attached to a chloromethyl group. Yet this small reagent became useful because the carbon-silicon bond does more than connect two fragments. Silicon changes the behavior of the neighboring carbon, and chemists can exploit that effect to generate reactive intermediates, install carbon units, and build alkenes.

The molecule can be written as (CH₃)₃SiCH₂Cl. The chloromethyl carbon behaves as an electrophilic site in substitution chemistry, so nucleophiles can replace chloride and attach a trimethylsilylmethyl group. But the resulting C-Si bond is not simply an inert protecting appendage. Fluoride has a strong affinity for silicon, and activation of silicon-containing intermediates can reveal carbon reactivity or drive elimination. The trimethylsilylmethyl unit can therefore carry latent reactivity through one operation and release it in another.

One historically important connection is Peterson olefination chemistry. Organosilicon reagents containing a carbon nucleophile adjacent to silicon can add to carbonyl compounds to form beta-hydroxysilanes, which then eliminate to give alkenes. Chloromethyltrimethylsilane provides access to useful organometallic or organosilicon building blocks through metal-halogen exchange and related transformations. A reagent that begins as a chloromethylsilane can therefore become part of a route to carbon-carbon double bonds.

The reagent also illustrates why silicon occupies a distinctive place in synthetic design. Carbon and silicon are in the same periodic group, yet silicon is larger, more electropositive, and forms exceptionally strong bonds to fluorine and oxygen. Those differences allow chemists to use a C-Si bond as a temporary handle: stable enough to survive selected steps but capable of activation under conditions that ordinary C-C bonds would not recognize. Modern organosilicon synthesis repeatedly exploits this combination of stability and triggerability.

This reactivity is especially useful because organosilicon groups can survive conditions that would destroy more reactive organometallic reagents. A chemist may therefore install the trimethylsilylmethyl fragment early, carry it through several operations, and activate it only when needed. Such sequencing is a recurring strategy in multistep synthesis: useful functionality is often not the group that reacts fastest, but the group whose reactivity can be postponed until the correct stage. Chloromethyltrimethylsilane is a compact example of that temporal control.

What makes chloromethyltrimethylsilane memorable is therefore not one final product. It is a lesson in reagent design. A chlorine atom supplies conventional electrophilic chemistry, while the neighboring trimethylsilyl group stores a second mode of reactivity for later use. The two halves can be addressed at different stages, turning a very small silane into a compact tool for constructing much larger organic structures.

References:

1. Hamann LG, Jones TK. (Chloromethyl)trimethylsilane. Encyclopedia of Reagents for Organic Synthesis. DOI: 10.1002/047084289X.rc129.

2. Peterson DJ. Journal of Organic Chemistry. 1968;33:780-784. DOI: 10.1021/jo01266a052.

3. PubChem. Silane, (chloromethyl)trimethyl-, CAS 2344-80-1.

4. Brook MA. Silicon in Organic, Organometallic, and Polymer Chemistry. Wiley, 2000.

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