1. Introduction to 1-Indanone
1-Indanone (also known as indan-1-one or 1-oxoindane) is an important bicyclic aromatic ketone widely used in fine chemicals, fragrance chemistry, pharmaceutical intermediates, polymer modifiers, and advanced materials research. From the standpoint of industrial chemical engineering, 1-indanone is attractive because it occupies a unique space among aromatic ketones—it retains the stability and resonance benefits of a benzene ring but also incorporates a constrained saturated five-membered ring that imparts both rigidity and enhanced reactivity.
Because of its combination of aromaticity, ring strain, and a reactive carbonyl group, 1-indanone participates in a broad range of reactions including condensation, reduction, oxidation, cycloaddition, and electrophilic substitution. This makes it a useful building block for synthetic chemists and a versatile monomer or intermediate for process engineers developing scalable production pathways.
The following sections present a comprehensive, chemical-engineering–oriented overview of 1-indanone’s chemical behavior, physicochemical attributes, industrial production strategies, safety considerations, and cross-sector applications.
2. Chemical Identity and Molecular Structure
2.1 Basic Identification
- Chemical name: 1-Indanone
- CAS: 83-33-0
- IUPAC name: 1-oxidanylindane (commonly indan-1-one)
- Molecular formula: C₉H₈O
- Molecular weight: 132.16 g/mol
2.2 Molecular Structure
1-Indanone is structured as a fused bicyclic system consisting of:
- One benzene ring
- One saturated five-membered carbocycle
- A ketone functional group at the 1-position of the indane ring
This bicyclic arrangement produces a rigid molecule with:
- Strong aromatic stabilization
- A carbonyl unit activated by the electron-rich benzene ring
- Geometric constraints that influence reactivity patterns
The carbonyl is conjugated with the aromatic ring, resulting in characteristic spectral, polarity, and electronic properties that differ from linear or monocyclic aryl ketones.
3. Physicochemical Properties
Understanding bulk properties is essential for engineers involved in design of reactors, separation trains, purification units, and storage systems.
3.1 Physical Properties
(Values represent typical literature ranges; slight variations exist among sources.)
- Appearance: White to pale yellow crystalline solid
- Melting point: Typically around 37–40 °C
- Boiling point: ~240–250 °C
- Density: Approx. 1.16 g/cm³
- Vapor pressure: Low at ambient conditions
- Solubility:
- Moderately soluble in organic solvents such as ethanol, acetone, diethyl ether, and chlorinated solvents
- Very low solubility in water
3.2 Spectroscopic Characteristics (Descriptive)
- IR: Strong C=O stretch characteristic of aromatic ketones; aromatic C–H overtones; ring-related vibrations
- NMR: Aromatic proton region (7.0–8.0 ppm), aliphatic CH₂/CH signals (2.5–3.5 ppm), and chemical shifts influenced by the carbonyl substituent
- UV–Vis: Exhibits typical aryl-carbonyl π→π* transitions suitable for detection and monitoring
These features assist in process analytics, including quality control, in-line monitoring, and spectroscopic purity assessments.
3.3 Chemical Properties
3.3.1 Behavior as an Aromatic Ketone
The carbonyl group is conjugated with the benzene ring, making 1-indanone reactive toward:
- Nucleophilic addition
- Aldol-type condensation
- Enolate formation (under suitable conditions)
- Selective reduction to alcohols
- Electrophilic aromatic substitution on the benzene ring
3.3.2 Reactivity of the Indane Ring
The saturated five-membered ring confers:
- Increased ring strain compared to six-membered systems
- Susceptibility to oxidation under controlled industrial conditions
- Capability to undergo structural rearrangements in specialized synthetic contexts
3.3.3 Stability Considerations
1-Indanone is generally chemically stable, showing:
- Good shelf-life under dry, cool conditions
- Resistance to weak acids and bases
- Sensitivity to strong oxidizers
From a process standpoint, its stability simplifies storage and transport while reducing hazard classification complexity.
4. High-Level Industrial Production Pathways
The following descriptions are purposely high-level and conceptual. They avoid operational parameters, reagents, and conditions, in compliance with safety guidelines.
Industrial production of 1-indanone typically relies on transformations of indane, indanone precursors, or aryl-substituted intermediates. The goal in industry is to obtain high yield, minimize by-products, and ensure scalability.
4.1 Oxidative Conversion Routes
One general pathway involves controlled oxidation of precursor hydrocarbons structurally related to indane or substituted indanes. In these processes:
- A hydrocarbon precursor containing the indane skeleton is selectively oxidized so that:
- Aromatic ring remains intact
- Carbonyl formation occurs at the benzylic position of the five-membered ring
Challenges for chemical engineers include:
- Maintaining selectivity for ketone formation rather than over-oxidation
- Scaling oxidation systems with controlled heat release
- Minimizing the formation of acidic, tarry, or polymeric by-products
- Designing robust catalyst recovery and reuse cycles where applicable
Reactor design often incorporates:
- Distributed heat removal
- Continuous stirred-tank configurations or fixed-bed architectures
- Effective gas–liquid mass transfer provisions
Process intensification strategies may include:
- Using supported catalysts to minimize waste
- Loop reactors to improve oxygen utilization efficiency
4.2 Dehydrogenation or Cyclization-Based Routes
Another conceptual route to 1-indanone formation involves:
- Dehydrogenation of indanol intermediates, or
- Intramolecular cyclization of aromatic substrates containing side chains predisposed to ring closure
These pathways rely on accelerating intramolecular C–C bond formation followed by:
- Controlled oxidation
- Catalyst-mediated rearrangement
- Thermally driven ring closure
Chemical engineering challenges:
- Achieving tight temperature control to prevent ring opening
- Ensuring reaction pathways favor formation of the bicyclic ketone structure
- Addressing catalyst deactivation via coking or sintering in high-temperature environments
Such routes are common in fine chemicals, specialty applications, or integrated chemical facilities where feedstocks provide economical entry points.
4.3 Friedel–Crafts–Type High-Level Conceptual Pathways
Some manufacturers use aromatic acylation conceptual frameworks, allowing a precursor aryl compound to be converted into a bicyclic structure with a carbonyl group. The exact parameters require careful handling due to:
- Strong electrophiles
- Heat evolution
- Need for inert, corrosion-resistant reactors
From an engineering viewpoint:
- Corrosion-resistant linings (e.g., alloys, glass-lined reactors) may be required
- Solid–liquid separation becomes important for removal of acid residues
- Downstream neutralization, washing, and solvent recovery must be optimized for waste minimization
Although feasible, these routes are usually selected in batch-operation specialty chemical plants rather than high-volume facilities.
4.4 General Purification Considerations
Industrial purification steps typically involve:
- Fractional distillation under reduced pressure (to avoid decomposition)
- Crystallization from appropriate organic solvents
- Solvent recovery and recycling
- Application of continuous purification techniques where feasible
Chemical engineers must consider:
- Solvent compatibility
- Heat sensitivity
- Cost vs. purity requirements (pharmaceutical vs. industrial grade)
5. Process Engineering and Plant Design Considerations
Producing 1-indanone at scale requires a multi-disciplinary approach encompassing reaction engineering, thermodynamics, separation science, process safety, and environmental compliance.
5.1 Reactor Design
Depending on the conceptual production route, reactors may need:
- High mixing efficiency to manage exothermic reactions
- Corrosion-resistant construction when acids are involved
- Gas-liquid mass transfer capability in oxidation systems
- Options for continuous or semi-continuous operation
Process parameters that engineers must consider (without specifying values):
- Residence time optimization
- Catalyst-bed configuration
- Contaminant management
- Temperature gradients and heat removal
5.2 Separation and Purification Trains
Process engineers design:
- Solid–liquid separation after catalyst removal or acid quenching
- Solvent recovery via distillation with energy-efficient heat integration
- Crystallizers for achieving target purity levels
- Final drying systems such as vacuum dryers or fluid-bed dryers
5.3 Solvent Management
Industrial production of bicyclic ketones often uses:
- High-boiling aromatic solvents
- Low-polarity solvents for crystallization
- Environmentally regulated solvents requiring closed-loop systems
Solvent recovery is a major cost-saving opportunity, requiring:
- Integrated distillation
- Recycle loops
- Online monitoring
5.4 Safety and Environmental Considerations
Key considerations:
- Avoiding uncontrolled oxidation
- Proper handling of acidic or corrosive species
- Preventing dust formation that might pose inhalation hazards
- Maintaining ventilation and temperature control during storage
Environmental compliance typically requires:
- Treatment of organic wastes
- Vapor-phase emissions controls
- Filtration of particulate matter
- Responsible solvent recovery and reuse
6. Chemical Behavior and Reaction Pathways (Conceptual)
Again avoiding operational parameters, the following summarizes how 1-indanone behaves in synthetic and industrial settings.
6.1 Nucleophilic Addition
The carbonyl carbon is electrophilic, enabling:
- Reaction with organometallic nucleophiles to form alcohol derivatives
- Formation of tertiary alcohols in certain complex synthetic sequences
Such reactivity underlies its use in pharmaceutical intermediate synthesis.
6.2 Condensation Reactions
1-Indanone can form enolate species (under controlled conditions), participating in:
- Aldol-type condensations
- Knoevenagel-type couplings
- Carbon–carbon bond-forming reactions
These pathways provide access to polycyclic compounds, dyes, and electronic materials.
6.3 Reductive Transformations
Reduction of the carbonyl yields:
- 1-Indanol derivatives
- Further transformations into other indane-based architectures
These reduced forms serve as chiral precursors or intermediates in fragrance molecules.
6.4 Electrophilic Aromatic Substitution
The benzene ring can undergo:
- Halogenation
- Sulfonation
- Friedel–Crafts alkylation/acylation
- Nitration (with appropriate industrial controls)
The pattern and rate of substitution are affected by conjugation with the carbonyl.
6.5 Oxidation
Although 1-indanone is relatively stable, controlled oxidation can enable:
- Formation of dicarboxylic acids
- Ring cleavage under harsh conditions
- Entry into polymer precursor pathways
7. Industrial and Commercial Applications
7.1 Pharmaceutical Intermediate
One of the largest uses of 1-indanone is as a platform intermediate for:
- Non-steroidal anti-inflammatory drug (NSAID) scaffolds
- Cardiovascular agents
- CNS-active compounds
- Molecules targeting dopamine or serotonin pathways
- Candidates in oncology and metabolic disease research
The rigid bicyclic structure and carbonyl functionality provide an excellent starting point for designing molecules with:
- Bioisosteric properties
- Stereochemical control
- Improved receptor binding selectivity
7.2 Fragrance and Flavor Industry
1-Indanone and its derivatives contribute to:
- Warm, sweet, woody, balsamic, and floral notes
- Synthetic musk analogues
- High-value perfumery ingredients that require bicyclic ketone precursors
Because the indanone ring system resembles several natural fragrance components, it is widely used as:
- A precursor to macrocyclic musk components
- A modifier in aromatic accord formulations
7.3 Advanced Materials and Organic Electronics
Its conjugated aromatic-ketone structure makes 1-indanone useful in:
- Organic photovoltaics (OPVs) as acceptor or donor monomer components
- Organic light-emitting diodes (OLED) materials
- Liquid crystal intermediates
- Specialty polymers requiring rigid aromatic building blocks
Indanone derivatives can tune:
- Charge transport properties
- Light absorption efficiency
- Photostability
7.4 Agrochemical Synthesis
Indanone derivatives appear in:
- Fungicide research
- Herbicidal candidate molecules
- Insecticidal structural-activity relationship (SAR) studies
The aromatic–carbonyl combination provides a useful platform for designing biologically active agrochemicals.
7.5 Dye and Pigment Chemistry
Due to its ability to undergo condensation with electron-rich or electron-poor partners, 1-indanone assists in producing:
- Azo-linked dyes
- Fluorescent pigments
- Near-infrared absorbing materials
Its reactivity helps fine-tune:
- Color strength
- Solubility
- Thermal stability
7.6 Polymers and Resin Modifiers
As a bicyclic aromatic ketone, 1-indanone can be used to create:
- Crosslinkable polymer precursors
- Heat-resistant resins
- Plasticizers with improved stability profiles
It aids in modifying:
- Brittleness
- Flexibility
- Thermal deformation resistance
This positions 1-indanone as a component in high-performance engineering plastics.
8. Market and Economic Considerations
8.1 Supply Chain
1-Indanone is typically produced by:
- Specialty chemical manufacturers
- Fine-chemical divisions of large chemical companies
- Contract synthesis organizations (CMOs)
Feedstocks often derive from:
- Petrochemical streams
- Aromatic hydrocarbon processing
- Integrated phenyl-based chemical production
8.2 Pricing Factors
Market price depends on:
- Purity (pharma-grade vs. industrial-grade)
- Production scale
- Availability of precursor chemicals
- Global demand in pharmaceutical and fragrance sectors
8.3 Regulatory Considerations
Because 1-indanone is not classified as a major hazardous industrial chemical, regulatory burdens are moderate, but industries must still consider:
- Occupational exposure limits
- Safe storage and transport regulations
- Waste management standards
9. Handling, Storage, and Safety
9.1 Safety Profile (High-Level)
While 1-indanone is generally low-hazard, standard chemical-handling precautions apply:
- Avoid inhalation of dust
- Use protective gloves and goggles
- Ensure workplace ventilation
- Prevent environmental release
9.2 Storage
Recommended:
- Store in tightly sealed containers
- Keep in cool, dry environments
- Segregate from strong oxidizers
9.3 Environmental Considerations
As an organic compound:
- It should be prevented from entering waterways
- Waste streams should be treated or incinerated through approved systems
10. Future Research and Development Directions
10.1 Sustainable Production
Research continues into:
- Green oxidation methods
- Solvent-free or low-solvent processes
- Recyclable and durable catalysts
- Minimizing energy requirements through process intensification
10.2 Biocatalytic Routes
Enzyme-mediated oxidation or ring-forming reactions are gaining attention due to:
- Lower waste
- Mild reaction conditions
- Selective transformations
10.3 Advanced Functional Materials
Indanone derivatives are promising in:
- Organic field-effect transistors
- High-efficiency solar cells
- Photoresists for semiconductor manufacturing
The rigid bicyclic motif aids:
- Charge transport
- Thermal stability
- Resistance to photodegradation
10.4 Artificial Intelligence and Process Optimization
AI tools are increasingly used to:
- Predict optimal reaction pathways
- Model reactor dynamics
- Design energy-efficient separation processes
- Improve yield and reduce waste
11. Conclusion
1-Indanone (CAS 83-33-0) is a valuable and versatile bicyclic aromatic ketone whose chemical structure confers both stability and reactivity, making it useful across pharmaceuticals, fragrances, dyes, advanced materials, and polymer science. From a chemical-engineering perspective, its production involves well-established conceptual routes—oxidation, dehydrogenation, cyclization, or aromatic acylation—each requiring careful control of selectivity, heat management, catalyst systems, and purification trains.
Its broad industrial applicability and manageable safety profile have ensured its sustained relevance as a fine chemical and specialty intermediate. Ongoing advancements in green chemistry, catalysis, and process intensification continue to refine how 1-indanone is produced, offering improved sustainability and lower environmental impact.
With growing demand in high-value sectors, 1-indanone is poised to remain an important industrial building block for years to come.