1,3-Dimethyladamantane
[CAS# 702-79-4]

Identification

• Classification: Chemical reagent >> Organic reagent >> Ester >> Methyl ester compound
• Name: 1,3-Dimethyladamantane
• Synonyms: 1,3-Dimethyltricyclo[3.3.1.1(3,7)]decane
• Molecular Formula: C₁₂H₂₀
• Molecular Weight: 164.29
• CAS Registry Number: 702-79-4
• EC Number: 211-870-8
• SMILES: CC12CC3CC(C1)CC(C3)(C2)C

Properties

• Density: 1.0±0.1 g/cm³ Calc.^*, 0.902 g/mL (Expl.)
• Melting point: -30 °C (Expl.)
• Boiling point: 199.9±7.0 °C 760 mmHg (Calc.)^*, 201 °C (Expl.)
• Flash point: 52.8 °C (Calc.)^*, 52 °C (Expl.)
• Index of refraction: 1.521 (Calc.)^*, 1.478 (Expl.)

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

Safety Data

• Hazard Symbols: GHS02 Warning
• Risk Statements: H226
• 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.	3	H226
Aspiration hazard	Asp. Tox.	1	H304
Skin irritation	Skin Irrit.	2	H315

Discovery and Applications

1,3-Dimethyladamantane is a substituted adamantane hydrocarbon in which two methyl groups are located at the 1- and 3-positions of the rigid tricyclic adamantane framework. Adamantane itself was first isolated from petroleum fractions in the early twentieth century and later synthesized in the laboratory, becoming an important model compound in cage hydrocarbon chemistry. The discovery of alkyl-substituted adamantanes, including 1,3-dimethyladamantane, followed systematic investigations into the reactivity, substitution patterns, and stability of the adamantane skeleton. These studies demonstrated that substitution at bridgehead positions could be achieved under controlled conditions, leading to a family of dimethyladamantane isomers with distinct structural and physical properties.

The synthesis of 1,3-dimethyladamantane is typically achieved through alkylation or rearrangement reactions starting from adamantane or related precursors. Early work showed that Lewis acid catalyzed methylation reactions could selectively introduce methyl groups onto the adamantane framework, although mixtures of isomers were often obtained. Advances in reaction control and separation techniques later enabled the isolation and characterization of specific dimethyladamantane isomers. Structural elucidation using spectroscopic methods confirmed the unique rigidity and symmetry of the 1,3-disubstituted compound, contributing to its role as a reference structure in hydrocarbon chemistry.

From an application perspective, 1,3-dimethyladamantane has primarily served as a research compound rather than a bulk industrial chemical. Its rigid, saturated cage structure makes it valuable as a model system for studying steric effects, conformational rigidity, and substituent influences in non-aromatic hydrocarbons. In physical organic chemistry, dimethyladamantanes have been used to investigate carbocation rearrangements and stability, since adamantyl cations exhibit unusual stability compared with acyclic analogues. These studies have helped clarify fundamental concepts related to hyperconjugation and three-dimensional bonding effects.

In materials and petrochemical research, substituted adamantanes including 1,3-dimethyladamantane have attracted interest as components of high-energy-density fuels and lubricants. The high thermal stability and compact structure of the adamantane core contribute to favorable volatility and resistance to thermal degradation. While 1,3-dimethyladamantane itself is not widely commercialized for such uses, it has been examined alongside other alkyladamantanes to understand how substitution patterns affect melting point, boiling point, and viscosity, information that is useful in the design of advanced hydrocarbon fluids.

Another area of application is analytical chemistry, where 1,3-dimethyladamantane has been used as a reference or calibration compound in gas chromatography and mass spectrometry. The well-defined fragmentation patterns of adamantane derivatives make them suitable for testing instrument performance and for studying structure–fragmentation relationships in mass spectrometric analysis. The presence of methyl substituents provides additional insight into how small structural changes influence ionization and fragmentation behavior.

Although many biologically active compounds are based on the adamantane framework, such as antiviral and neurological drugs, 1,3-dimethyladamantane itself has not been developed as a pharmaceutical agent. Instead, its importance lies in providing a chemically inert and structurally rigid scaffold that informs the design and understanding of more complex functionalized adamantane derivatives. Research on dimethyladamantanes has therefore contributed indirectly to medicinal chemistry by expanding knowledge of how substituents can be positioned on the adamantane core without compromising stability.

Overall, 1,3-dimethyladamantane represents a well-defined member of the substituted adamantane family whose discovery arose from fundamental studies of cage hydrocarbons. Its applications are mainly in research contexts, including physical organic chemistry, materials science, and analytical method development. Through these roles, it continues to support a deeper understanding of structure–property relationships in rigid hydrocarbon systems.

References

Bagrii, E. I., Nekhaev, A. I. & Maksimov, A. L. (2017). Oxidative functionalization of adamantanes (review). Petroleum Chemistry, 57, 169–184. https://doi.org/10.1134/s0965544117020128

Khusnutdinov, R. I., Shchadneva, N. A. & Khisamova, L. F. (2015). Bromination of adamantane and its derivatives with tetrabromomethane catalyzed by iron compounds. Russian Journal of Organic Chemistry, 51, 223–229. https://doi.org/10.1134/s1070428015020074

Baranov, N. I., Bagrii, E. I., Safir, R. E., Cherednichenko, A. G., Bozhenko, K. V. & Maksimov, A. L. (2024). Quantum-chemical study of formation of alkyl- and alkenyladamantanes by ionic alkylation with olefins. Kinetics and Catalysis, 65, 123–132. https://doi.org/10.1134/s0023158423601171