3,3-Dimethoxybutan-2-one
[CAS 21983-72-2]

Identification

• Classification: Organic raw materials >> Ketone compound
• Name: 3,3-Dimethoxybutan-2-one
• Synonyms: 3,3-Dimethoxy-2-butanone
• Molecular Formula: C₆H₁₂O₃
• Molecular Weight: 132.16
• CAS Registry Number: 21983-72-2
• EC Number: 629-346-6
• SMILES: CC(=O)C(C)(OC)OC

Properties

• Density: 1.0±0.1 g/cm³ Calc.^*, 0.987 g/mL (Expl.)
• Boiling point: 145.5 °C 760 mmHg (Calc.)^*, 145 - 146 °C (Expl.)
• Flash point: 45.0 °C (Calc.)^*, 45 °C (Expl.)
• Index of refraction: 1.4 (Calc.)^*

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

Safety Data

• Hazard Symbols: GHS02 WarningGHS02
• 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
Skin irritation	Skin Irrit.	2	H315
Specific target organ toxicity - single exposure	STOT SE	3	H335
Eye irritation	Eye Irrit.	2	H319
Acute toxicity	Acute Tox.	4	H302
Acute toxicity	Acute Tox.	4	H332
Eye irritation	Eye Irrit.	2A	H319
Acute toxicity	Acute Tox.	4	H312

• Transport Information: UN 1224

Discovery and Applications

3,3-Dimethoxybutan-2-one is an aliphatic ketone containing a ketone functional group and a geminal dimethoxy acetal-like carbon center. It belongs to the class of oxygenated carbonyl compounds and is characterized by the coexistence of a reactive carbonyl group and two ether substituents attached to the same carbon atom.

The molecular structure consists of a four-carbon chain containing a ketone group at the 2-position and two methoxy groups attached to the adjacent 3-position carbon. The carbon skeleton can be described as a butan-2-one framework in which the carbon at position 3 carries two methoxy substituents. This arrangement gives the molecule both carbonyl and acetal-related structural features.

The ketone functional group contains a carbonyl carbon that is sp²-hybridized and adopts trigonal planar geometry. The carbon–oxygen double bond is strongly polarized because oxygen is more electronegative than carbon. The carbonyl oxygen carries a partial negative charge and acts as a hydrogen bond acceptor, while the carbonyl carbon is electrophilic and susceptible to nucleophilic attack.

The carbon atom bearing the two methoxy groups is sp³-hybridized and has tetrahedral geometry. Each methoxy group consists of an oxygen atom bonded to a methyl group. The ether oxygen atoms contain lone pairs of electrons and function as hydrogen bond acceptors but cannot donate hydrogen bonds because they lack O–H bonds.

The presence of two methoxy substituents on the same carbon creates an acetal-like environment. However, because the molecule also contains a separate ketone carbonyl group, it is not a simple acetal derived from the same carbonyl functionality. The adjacent arrangement of oxygen substituents influences electron distribution and steric properties around the carbon skeleton.

From an electronic perspective, the methoxy groups exert electron-donating effects through the oxygen atoms, while the ketone group withdraws electron density through the carbonyl system. These opposing effects influence the polarization of the molecule and contribute to its overall reactivity.

The carbon atoms in the methyl and methoxy groups are sp³-hybridized, allowing free rotation around single bonds. This gives the molecule conformational flexibility compared with rigid aromatic or cyclic compounds. The compact structure and absence of extended conjugation limit electronic delocalization beyond the carbonyl group.

Physicochemically, 3,3-dimethoxybutan-2-one is a polar organic molecule. The ketone carbonyl and two ether oxygen atoms provide multiple hydrogen bond acceptor sites, increasing interactions with polar solvents. However, the methyl groups contribute hydrophobic character, giving the molecule a balance between polar and nonpolar features.

The molecule does not contain hydrogen bond donor groups because it lacks hydroxyl, amino, or other functional groups containing transferable hydrogen atoms. Its intermolecular interactions are therefore dominated by dipole–dipole interactions involving oxygen atoms and by dispersion forces from the hydrocarbon portions.

Chemically, the ketone carbonyl is the primary reactive center. It can undergo nucleophilic addition reactions, reduction to the corresponding alcohol, and condensation reactions under suitable conditions. The carbon adjacent to the carbonyl group may participate in reactions involving enolate formation if sufficiently acidic hydrogen atoms are available.

The methoxy groups are relatively stable ether functionalities under neutral conditions. Under strongly acidic conditions, ether cleavage may occur, particularly in the presence of strong protonating agents, producing alcohol-derived fragments and other oxygenated products.

The molecule’s acetal-like carbon center can influence its stability and reactivity by modifying the electronic environment of the carbon chain. The oxygen substituents increase polarity and can stabilize certain reaction intermediates through inductive effects.

Overall, 3,3-dimethoxybutan-2-one is an oxygen-rich aliphatic ketone containing a reactive carbonyl group and a geminal dimethoxy-substituted carbon center. Its combination of carbonyl reactivity, ether functionality, and flexible saturated structure defines its chemical behavior and makes it a representative member of functionalized aliphatic ketone derivatives.

References

2021. Effect of the nature of a fluorinated substituent on the synthesis of functionalized 1,3-diketones. Russian Chemical Bulletin.
DOI: 10.1007/s11172-021-3145-z

2019. Studies on Proximate Composition and Phytochemical Profiling of Turbinaria ornata and its Antiproliferative Effect on Y79 Cell Lines. Thalassas: An International Journal of Marine Sciences.
DOI: 10.1007/s41208-019-00159-x

2018. Intramolecular cyclization of lithium 4,4-dimethoxy-1-(perfluoroalkyl)pentane-1,3-dionates on treatment with boron trifluoride diethyl etherate. Russian Chemical Bulletin.
DOI: 10.1007/s11172-018-2099-2