2-Chloro-2-methylpropane
[CAS# 507-20-0]

Identification

• Classification: Chemical reagent >> Organic reagent >> Halogenated aliphatic hydrocarbon
• Name: 2-Chloro-2-methylpropane
• Synonyms: 2-Chloro-2-methyl propane; tert-Butyl chloride; Trimethylchloromethane
• Molecular Formula: C₄H₉Cl
• Molecular Weight: 92.57
• CAS Registry Number: 507-20-0
• EC Number: 208-066-4
• SMILES: CC(C)(C)Cl

Properties

• Density: 0.9±0.1 g/cm³ Calc.^*, 0.851 g/mL (Expl.)
• Melting point: -25 °C (Expl.)
• Boiling point: 50.6 °C 760 mmHg (Calc.)^*, 51 - 52 °C (Expl.)
• Flash point: 18.3 °C (Calc.)^*, -23 °C (Expl.)
• Solubility: water slightly soluble (Expl.)
• Index of refraction: 1.395 (Calc.)^*, 1.385 (Expl.)

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

Safety Data

• Hazard Symbols: GHS02 Danger
• Risk Statements: H225
• Safety Statements: P210-P233-P240-P241-P242-P243-P280-P303+P361+P353-P370+P378-P403+P235-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Flammable liquids	Flam. Liq.	2	H225
Acute toxicity	Acute Tox.	4	H302
Specific target organ toxicity - single exposure	STOT SE	3	H335
Carcinogenicity	Carc.	2	H351
Eye irritation	Eye Irrit.	2	H319
Skin irritation	Skin Irrit.	2	H315

• Transport Information: UN 1127

Discovery and Applications

2-Chloro-2-methylpropane, also known as tert-butyl chloride, is a branched alkyl halide with the molecular formula C₄H₉Cl. It appears as a colorless, flammable liquid with a characteristic odor and is recognized for its role as a reactive intermediate in organic synthesis. The compound consists of a chlorine atom bonded to a tertiary carbon, which is connected to three methyl groups, making it highly susceptible to nucleophilic substitution and elimination reactions.

The compound was first synthesized in the 19th century through the chlorination of tert-butyl alcohol with hydrogen chloride under controlled conditions. The tertiary carbon structure stabilizes the carbocation intermediate, facilitating S_N1-type reactions and making the compound an important model for studying carbocation chemistry and reaction mechanisms in branched systems. Industrial preparation focuses on optimizing yield while minimizing side reactions such as rearrangement or elimination to form isobutylene.

Chemically, 2-chloro-2-methylpropane is used extensively as a precursor for tert-butyl derivatives in both laboratory and industrial settings. Its reactivity allows for the formation of ethers, amines, esters, and other functional groups through nucleophilic substitution. The tertiary nature of the carbon center favors S_N1 reactions over S_N2, providing selective pathways for synthesis. This property is particularly valuable in preparing compounds that require minimal steric hindrance during substitution.

One of the main industrial applications of 2-chloro-2-methylpropane is in the production of tert-butyl ethers, such as methyl tert-butyl ether (MTBE), which historically served as a gasoline additive to increase octane rating and improve combustion efficiency. It is also employed in synthesizing antioxidants, stabilizers, and other specialty chemicals where the tert-butyl group imparts steric bulk and influences reactivity, solubility, and stability of the resulting molecules.

In pharmaceutical chemistry, 2-chloro-2-methylpropane functions as a key intermediate in the synthesis of various active pharmaceutical ingredients. Its ability to introduce a bulky tert-butyl group into molecules can enhance metabolic stability and modify lipophilicity, contributing to improved pharmacokinetic properties. Similarly, it is used in agrochemical applications to prepare herbicides, pesticides, and other crop protection agents, where the tert-butyl moiety helps tailor molecular behavior and efficacy.

Mechanistically, the tertiary chloride provides a valuable system for studying carbocation formation and the influence of steric and electronic effects on reaction kinetics. Its behavior under acidic and nucleophilic conditions offers insight into reaction pathways and the development of selective synthetic strategies. The compound’s volatility and moderate boiling point also facilitate its use in vapor-phase reactions and distillation processes.

Physically, 2-chloro-2-methylpropane is insoluble in water but miscible with most organic solvents, including ethers, alcohols, and hydrocarbons. It exhibits a relatively low vapor pressure and is flammable, requiring careful handling in laboratory and industrial environments. Exposure precautions include using gloves, eye protection, and proper ventilation, as the compound can cause irritation and adverse health effects if inhaled or absorbed. Environmental considerations focus on preventing release into water and soil due to its potential toxicity.

The discovery and utilization of 2-chloro-2-methylpropane highlight its significance as a reactive tertiary alkyl halide. Its chemical versatility, ability to undergo selective substitution reactions, and functional role in the synthesis of ethers, pharmaceuticals, and specialty chemicals ensure its ongoing importance in organic chemistry and industrial applications.

References

2022. A Review on the Halodefluorination of Aliphatic Fluorides. Synthesis, 54(4).
DOI: 10.1055/a-1684-0121

2025. Mechanochemical activation of metallic lithium for the generation and application of organolithium compounds in air. Nature Synthesis, 4(3).
DOI: 10.1038/s44160-025-00753-3

2023. A highly ionic reaction environment achieving low-temperature polyethylene upcycling. Science China Chemistry, 66(6).
DOI: 10.1007/s11426-023-1561-y