Acetal
[CAS# 105-57-7]

Identification

• Classification: Organic raw materials >> Aldehyde
• Name: Acetal
• Synonyms: 1,1-Diethoxyacetal; 1,1-Diethoxyethane; Acetaldehyde diethyl acetal
• Molecular Formula: C₆H₁₄O₂
• Molecular Weight: 118.17
• CAS Registry Number: 105-57-7
• EC Number: 203-310-6
• FEMA: 2002
• SMILES: CCOC(C)OCC

Properties

• Density: 0.825
• Melting point: -100 °C
• Boiling point: 103 °C
• Refractive index: 1.379-1.385
• Flash point: -21 °C
• Water solubility: 46 g/L (25 °C)

Safety Data

• Hazard Symbols: GHS02;GHS07 Danger
• Risk Statements: H225-H315-H319
• Safety Statements: P210-P233-P240-P241-P242-P243-P264-P264+P265-P280-P302+P352-P303+P361+P353-P305+P351+P338-P321-P332+P317-P337+P317-P362+P364-P370+P378-P403+P235-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Skin irritation	Skin Irrit.	2	H315
Flammable liquids	Flam. Liq.	2	H225
Eye irritation	Eye Irrit.	2	H319
Skin sensitization	Skin Sens.	1	H317
Flammable liquids	Flam. Liq.	1	H224
Skin corrosion	Skin Corr.	1	H314
Serious eye damage	Eye Dam.	1	H318

• Transport Information: UN 1088

Discovery and Applications

Acetal, an organic compound type characterized by the general formula R₂C(OR')₂, is central in organic chemistry and industrial applications. Acetals were first studied in the 19th century as chemists began investigating compounds capable of protecting functional groups in complex synthesis processes. The term "acetal" commonly refers to any compound where two alkoxy groups are bonded to a single carbon atom, stemming from initial studies on acetaldehyde derivatives. The reactivity and stability of acetal linkages in both synthetic and biological systems have established acetals as valuable compounds in multiple fields.

Structurally, acetals contain a carbon atom connected to two ether (–OR) groups and one or two alkyl (R) or aryl (Ar) groups. This configuration makes acetals highly stable under neutral or basic conditions, although they readily decompose in acidic environments. Acetals can be synthesized through the acid-catalyzed reaction of an aldehyde or ketone with an alcohol, forming a hemiacetal intermediate, which subsequently reacts with another alcohol molecule to yield the final acetal structure. This reactivity has made acetals valuable as protective groups in organic synthesis, shielding sensitive carbonyl groups during multi-step reactions.

In industrial and commercial contexts, acetals play critical roles in materials and manufacturing. Polyoxymethylene (POM), also known as acetal resin, is a widely used thermoplastic derived from formaldehyde, with applications spanning automotive components, consumer electronics, and precision parts. Due to its high strength, low friction, and excellent chemical resistance, acetal resin is used in manufacturing gears, fasteners, and bearing surfaces. In food packaging and medical devices, acetals are valued for their stability and low moisture absorption, which ensure the longevity and safety of end products.

Beyond manufacturing, acetals also serve in perfumery and pharmaceuticals, where they are synthesized to encapsulate and release fragrances and medicinal compounds gradually. Acetals derived from natural or synthetic aldehydes and alcohols are also used as flavoring agents due to their stability and pleasant aromas, contributing to the sensory qualities of food and beverages. Their stability and relatively low toxicity make them suitable for various consumer products, though regulatory standards govern their use, particularly in consumables.

The discovery and utilization of acetals have made a lasting impact across chemistry and industry. Their protective qualities in synthetic chemistry, resilience in materials, and contribution to consumer products reflect the versatility and ongoing relevance of acetal compounds in modern applications.

References

2024. Preparative scalable method for the synthesis of cyclic and acyclic acetals of chloropropiolaldehyde and their transformation into acetals of lithiumpropiolaldehyde. Russian Chemical Bulletin, 73(10), 2607-2614.
DOI: 10.1007/s11172-024-4428-y
2013. In(III)/PhCO2H Binary Acid Catalyzed Tandem [2 + 2] Cycloaddition and Nazarov Reaction between Alkynes and Acetals. Organic Letters, 15(16), 4182-4185.
DOI: 10.1021/ol4020464
2010. Direct Aerobic Photo-Oxidative Synthesis of Aromatic Methyl Esters from Methyl Aromatics via Dimethyl Acetals. Organic Letters, 12(15), 3494-3497.
DOI: 10.1021/ol1014575