This compound belongs to the class of organic compounds known as benzene and substituted derivatives. These are aromatic compounds containing one monocyclic ring system consisting of benzene.
External Descriptors
Not available
1. Djoumbou Feunang Y, Eisner R, Knox C, Chepelev L, Hastings J, Owen G, Fahy E, Steinbeck C, Subramanian S, Bolton E, Greiner R, and Wishart DS. ClassyFire: Automated Chemical Classification With A Comprehensive, Computable Taxonomy. Journal of Cheminformatics, 2016, 8:61.
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Application Protocols
No assay/application protocols are provided for this item. As a general synthetic reagent, procedures depend on the intended transformation (e.g., urea or carbamate formation). See the Reaction Conditions and Synthetic Utility sections for practical guidance and adapt to your substrates and scale.
Item-specific testing recommendations: Not specified for this item; refer to CoA/Spec Sheet.
Biological Roles
This compound is a synthetic aryl isocyanate used as a chemical building block, not a natural metabolite. No inherent biological role is assigned.
General biochemical considerations for isocyanates (literature; not product claims):
Protein reactivity: Isocyanates acylate nucleophilic residues (primarily lysine ε-NH2, also cysteine and serine under some conditions) to form stable urea/carbamate adducts. This underlies sensitization potential and utility in bioconjugation chemistry under controlled conditions.
Hydrolysis in aqueous media: Rapid reaction with water forms unstable carbamic acids that decarboxylate to amines and CO2; thus, sustained presence in biological systems is unlikely without continuous exposure.
Stability/selectivity: Aryl isocyanates are generally less volatile than aliphatic analogs; reactivity can be tuned by ring substituents (para-ethyl modestly increases hydrophobicity, potentially affecting membrane association in model systems).
Use context: Any biological interaction studies should be conducted in vitro under controlled laboratory conditions with appropriate containment and quenching protocols. No medical, diagnostic, or therapeutic applications are implied or supported. Research Use Only.
Buffer Applications
Not typically applicable. 4-Ethylphenyl isocyanate reacts with water and amine-containing buffers, making it unsuitable as a buffering component or for routine use in aqueous buffer systems.
Practical note: If conducting aqueous or biphasic derivatizations (e.g., labeling amines on a solid support), strictly control pH and exclude bulk water—use aprotic organic solvents or minimal-water systems and quench unreacted isocyanate promptly.
Green Alternatives
While aryl isocyanates are efficient electrophiles, they pose sensitization hazards and are moisture-reactive. Consider greener or safer-by-design approaches when possible.
Alternatives to direct isocyanate use (literature/guidance):
Carbonyl diimidazole (CDI) urea synthesis: Couple amines via CDI activation to form ureas without free isocyanates. Typically done in MeCN/DMF at ambient temperature; byproduct is imidazole (benign, easily removed).
Carbamate formation via cyclic carbonates: Transcarbonation (e.g., dimethyl/diethyl carbonate or ethylene carbonate) with alcohols/amines under catalysis avoids isocyanates; CO2-derivative feedstocks considered greener.
Curtius/Hofmann-type routes in situ: Generate isocyanates transiently under containment (e.g., from acyl azides) and trap immediately with nucleophiles, minimizing operator exposure. Requires careful safety controls.
Enzymatic urethane formation (emerging): Lipase-catalyzed coupling of carbonates with alcohols in green solvents (e.g., 2-MeTHF), suitable for delicate substrates.
Comparison snapshot (general; not item-specific):
Direct aryl isocyanate
Pros: Fast, high atom economy; mild conditions; broad scope.
Pros: Isocyanate-free; benign byproducts; safer handling.
Cons: Extra step; imidazole removal; not ideal for sterically hindered substrates.
Carbonate routes
Pros: Greener reagents/solvents; scalable.
Cons: Often higher temperature/catalyst; selectivity considerations.
Process suggestions: If isocyanates are required, employ greener solvents (2-MeTHF, CPME, toluene), microdosing, and closed transfers to reduce emissions and exposure.
Pharmaceutical Uses
No pharmacopeial/compendial status is indicated for this item. Not specified for this item; refer to CoA/Spec Sheet for any regulatory notes.
General formulation/manufacturing context (literature; not therapeutic claims):
Role as an intermediate: Aryl isocyanates are widely used to synthesize urea and carbamate linkages in drug discovery intermediates, linkers, and protecting groups. The para-ethylphenyl moiety can modulate lipophilicity and metabolic stability in SAR campaigns.
Excipient status: Not used as an excipient due to sensitization hazard and reactivity.
Process considerations: When used in GMP settings as an intermediate reagent, typical controls include residual isocyanate testing in intermediates, purge studies for aniline/urea/solvent residues, and validated quench procedures (alcoholic quench or aqueous ammonia under containment).
Green chemistry in process design: Favor closed transfers, minimal excess, and on-demand generation (in situ) when feasible to reduce operator exposure and waste.
All uses are for research and development/manufacturing of intermediates under appropriate controls. Not for human or veterinary use.
Physical Properties
Item-specific specifications (this lot): Not specified for this item; refer to CoA/Spec Sheet.
Literature/general properties for 4-ethylphenyl isocyanate (for reference only; not product specifications):
Physical state: typically a colorless to pale yellow liquid; may darken upon storage due to trace hydrolysis/polymerization.
Boiling point: aryl isocyanates generally boil in the ~190–230 °C range; p-ethyl substitution increases BP relative to phenyl isocyanate (~165–167 °C, literature). Specific BP for this isomer is reported in the ~200+ °C range across catalogs; consult primary references for an exact value.
Density (20–25 °C): aryl isocyanates commonly ~1.0–1.1 g/mL (literature). Exact value for this compound should be verified from the CoA.
Refractive index: Not specified for this item; refer to CoA/Spec Sheet.
Solubility: miscible with common organic solvents (aromatics, chlorinated solvents, ethers, ketones); reacts with protic solvents (alcohols, water) to form carbamates/carbamic acids.
Vapor pressure: low at ambient temperature (literature, typical for higher-boiling aryl isocyanates).
LogP: expected to be >2 due to aryl core and ethyl substituent (literature trend for aryl isocyanates), but item-specific value is not provided.
Notes
Handle under dry, inert atmosphere; even trace moisture leads to CO2 evolution and urea formation (dimerization via carbamic acid/amine).
Quality and Grades
Grade/Purity (item-specific): Not specified for this item; refer to CoA/Spec Sheet for exact purity, assay method, and impurity profile.
Context and expectations for aryl isocyanate quality (general guidance):
Typical analytical controls: GC purity (to monitor residual aniline/urea byproducts), water content by Karl Fischer (moisture critically impacts performance), and color/APHA. For chromatography-focused uses, UV background may be noted, though this material is typically a reagent/building block rather than a solvent.
Stabilization: Many commercial aryl isocyanates are shipped under inert gas and kept dry to suppress hydrolysis and urea formation. No inhibitor/stabilizer is indicated for this item; if present, it would be disclosed on the CoA. Absent such disclosure, assume “neat under inert” handling.
What the grade implies in practice:
Synthetic reliability: Low moisture and low amine/urea content are essential to achieve high conversions in urea/carbamate formation.
Chromatographic cleanliness: Lower non-volatile residue (NVR) and color ensure easier purification of target ureas/carbamates.
Recommendations:
Verify water and amine content on receipt if your application is moisture-sensitive or catalytic.
Record baseline GC and color; slight darkening over time is common with isocyanates and correlates with trace hydrolysis—recondition by microfiltration if needed and approved by your QA.
Always defer to the supplied CoA/SDS for authoritative specifications and acceptance criteria.
Reaction and Applications
4-Ethylphenyl isocyanate is a versatile electrophile for installing the 4-ethylphenyl carbamoyl (urea/carbamate) motif.
Common transformations (literature/general):
Urea formation: Rapid addition to primary/secondary amines at 0–25 °C gives N-(4-ethylphenyl)ureas. Secondary amines often proceed cleanly in DCM/THF with mild base (Et3N) if needed. For less nucleophilic anilines, heat (50–90 °C) in toluene/xylenes accelerates.
Carbamate (urethane) formation: Alcohols add across the isocyanate in the presence of catalytic base (DBU, TBD, DABCO) or organotin catalysts; useful for prodrug-like protecting groups in discovery chemistry and for polymer end-capping.
Thiocarbamates/thioureas: Thiols and thioamines react analogously, typically faster than O- or N-nucleophiles. Control odor and oxidation of thiols.
Polymer/oligomer end-capping: Reaction with diols/diamines yields urethane/urea linkages on macromers; aryl isocyanates can modulate Tg and hydrophobicity.
Surface/labile labeling: Isocyanates can derivatize surface amines (e.g., silica/aminoresins) creating robust urea linkages for solid-phase capture.
Practical tips:
Exotherm management: Dose isocyanate into cooled nucleophile solution; keep local concentration low.
Moisture scrubbing: Trace water will consume reagent to form 4-ethylphenyl urea (dimer). Dry glassware/solvents and maintain an inert blanket.
Monitoring: FTIR is diagnostic—strong NCO stretch ~2265–2275 cm⁻¹ disappears on conversion; urea C=O appears ~1630–1690 cm⁻¹.
Side reactions: With excess amine, bis-urea formation and allophanate/biuret products can occur; maintain near-stoichiometric conditions.
Reaction Conditions
General guidance for common couplings with aryl isocyanates (literature; adapt to substrate and scale):
Urea formation (amine + isocyanate)
Solvent: DCM, THF, toluene, MeCN (anhydrous).
Temperature: 0–25 °C for aliphatic amines; 40–90 °C for less nucleophilic anilines.
Base: Often unnecessary; add Et3N or DIPEA (0.1–0.5 equiv) to neutralize adventitious acid or improve sluggish cases.
Stoichiometry: 1.0–1.05 equiv isocyanate to minimize bis-addition; add isocyanate slowly to amine.
Time/Yield: Minutes to a few hours; typically high yields (70–95%, literature) with clean workups.
Catalyst: DBU/TBD/DABCO (1–10 mol%) or organotin catalysts for hindered systems.
Temperature: 20–80 °C depending on nucleophile.
Notes: Remove CO2 formed from moisture by inert sweep; for phenols, stronger base (NaH) in THF may be employed, then add isocyanate at 0 °C.
Thiourea formation (thioamines) and thiocarbamates (thiols)
Fast at RT in aprotic solvents; consider 0 °C start to control exotherm.
Workup tips:
Quench residual isocyanate with MeOH or dilute amine under cooling before aqueous workup.
Monitor by IR (NCO band) or LC/GC. Avoid silica containing residual water; pre-dry columns or add base modifier (0.1% Et3N) to prevent streaking/decomposition.
Safety: Maintain inert atmosphere throughout; vent CO2 cautiously. Consult SDS for scale-up hazards.
Safety and Handling
Item-specific GHS/labels: Not specified for this item; refer to SDS for definitive classification, H/P statements, and pictograms.
General isocyanate safety (literature/guidance; not product labeling):
Hazard profile: Isocyanates are potent respiratory/skin sensitizers; cause skin and eye irritation; harmful if inhaled. Aryl isocyanates can release CO2 and amines upon hydrolysis.
PPE: Use chemical-resistant gloves (e.g., nitrile, double-gloving recommended), lab coat, splash goggles. Employ a certified chemical fume hood. Consider a full-face respirator or supplied-air protection when aerosol formation or large-scale handling is possible (as per SDS/risk assessment).
Engineering controls: Strictly anhydrous technique; dry glassware. Use inert gas blanket (argon/nitrogen). Avoid open transfers and heated operations that could generate vapor.
Incompatibilities: Moisture, alcohols, amines (vigorous exotherm), strong bases (accelerated reactions), acids (may catalyze side reactions), oxidizers. Avoid contact with copper alloys that can catalyze decomposition.
First aid (overview; consult SDS):
Inhalation: Move to fresh air, keep warm/rest. Seek medical attention immediately.
Skin contact: Remove contaminated clothing. Wash with soap and water for ≥15 min. Seek medical attention if irritation persists.
Eye contact: Rinse with water for ≥15 min; remove contact lenses if easy; obtain medical attention.
Ingestion: Rinse mouth; do not induce vomiting; seek medical attention.
Spill/response: Contain under inert atmosphere; absorb with inert material (vermiculite). Quench residues cautiously with alcohol only in a controlled, cooled setup following SDS guidance.
Fire: Use dry chemical, CO2, or foam. Thermal decomposition can release toxic fumes (NOx, CO, HCN).
Solvent Selection
This product is a reactive aryl isocyanate (a reagent), not a process solvent. Solvent choice should prioritize dryness, substrate solubility, and control of exotherm when reacting with nucleophiles.
General solvent compatibility (literature/guidance):
Protic solvents: Alcohols and water react with isocyanates (forming carbamates and amines/CO2 respectively). Use only when deliberate reaction with the solvent is intended.
Polar aprotic vs aromatic media: Polar aprotics (MeCN, DMF) accelerate reactions with amines; aromatics (toluene) are useful for higher-temperature operations and for substrates sensitive to polar media.
Selection tips:
Urea formation (amine + isocyanate): DCM, THF, or toluene at 0–25 °C for exotherm control. Add isocyanate last to a cooled amine solution.
Carbamate formation (alcohol + isocyanate): Often toluene or THF with a catalytic base (e.g., DBU, Et3N) or organotin/tertiary amine catalysts, rigorously dry.
Heterogeneous systems: Add a phase-transfer base or switch to a more polar aprotic solvent (MeCN) to dissolve salts.
Comparison (general):
Toluene: good thermal window, low polarity; slower but cleaner.
DCM: excellent heat removal; low boiling point; handle under inert to limit HCl pickup/moisture.
THF/2-MeTHF: improved nucleophile solubility; ensure peroxide-free and anhydrous.
Storage and Reconstitution
Storage conditions (item-specific from Product Data): Store at 2–8 °C, argon charged. Shipped on wet ice.
Container/atmosphere: Keep tightly closed under an inert gas blanket (argon recommended). Use a septum-sealed bottle where feasible to enable inert transfers.
Moisture exclusion: Extremely important. Dry the bottle exterior before opening; purge headspace with argon after each use. Avoid repeated warm/cold cycling that may draw in humid air.
Handling practice:
Use dry glassware and anhydrous solvents. Conduct additions via syringe or cannula under positive argon pressure.
If solidification or increased viscosity occurs at low temperature, warm gently to ambient under inert gas before dispensing.
Stability: Aryl isocyanates can slowly hydrolyze or dimerize to ureas upon moisture exposure, leading to color change and reduced assay. Check by IR (NCO band ~2265–2275 cm⁻¹) or GC before critical uses.
Reconstitution: Not applicable; supplied neat. If dilution is required for dosing, prepare anhydrous stock solutions (e.g., in toluene, DCM, or THF) immediately before use and store short-term at 2–8 °C under argon.
Disposal: Quench residues under controlled, cooled conditions with alcohol (e.g., MeOH) or dilute amine, then follow institutional hazardous waste procedures.
Research Use Only. Always consult the SDS/CoA for definitive guidance.
Structure and Identity
4-Ethylphenyl isocyanate is an aryl isocyanate bearing a para-ethyl substituent on the phenyl ring. The electrophilic –N=C=O group is conjugated to the aromatic ring, enhancing reactivity toward nucleophiles.
Item identifiers (from Product Data)
SKU: E156038
CAS: 23138-50-3
InChIKey: 94149 (as provided)
Category: Chemical and Biochemical Reagents (research use only)
Literature/Computed identity (general reference; not item-specific specs)
Molecular formula (literature): C9H9NO
Molecular weight (literature): ~147.17 g/mol
Preferred IUPAC name (literature): 1-ethyl-4-isocyanatobenzene (para-ethylphenyl isocyanate)
SMILES (literature): O=C=Nc1ccc(CC)cc1
Structural features (general chemistry)
Functional group: aryl isocyanate (–N=C=O), strongly electrophilic at the carbon of the isocyanate.
Ring system: monosubstituted para-ethylbenzene core.
Connectivity description (2D): a benzene ring bearing an ethyl substituent at the para position relative to an isocyanate substituent attached via nitrogen (Ar–N=C=O).
Stereochemistry: none (achiral).
Synthetic Utility
Key functional group: aryl isocyanate (–N=C=O), an ambident electrophile with dominant reactivity at the carbonyl carbon. The para-ethyl substituent provides a hydrophobic aryl handle that can influence binding in medicinal chemistry and material properties in polymer science.
Transformations (literature/general):
Nucleophilic additions
Amines → ureas (fast, often quantitative under mild conditions).
Alcohols/phenols → carbamates (base- or catalyst-assisted).
Thiols → thiocarbamates (very rapid; useful for click-like assembly under dry conditions).
Secondary reactions
Allophanate/biuret formation under excess isocyanate or at elevated temperature; control stoichiometry.
Hydrolysis → amine + CO2 via carbamic acid intermediate; scrubbers may be needed on scale.
Crosslinking: Reaction with di- or poly-functional nucleophiles yields urea/urethane networks; aryl isocyanates can serve as end-cappers or crosslink nodes.
Retrosynthetic perspective:
Installing the 4-ethylphenyl urea motif via direct coupling is often more efficient than phosgene/CDI routes to symmetric ureas. For unsymmetrical ureas, sequential addition strategies (amine A + aryl isocyanate, then amine B via carbonyl activation) provide control.
Analytical handles:
IR: strong NCO band ~2265–2275 cm⁻¹; disappearance indicates conversion.
13C NMR: isocyanate carbon around 122–130 ppm (N=C=O central carbon) and 150–160+ ppm for carbonyl, depending on solvent; urea carbonyl shifts to ~155–165 ppm.
Target Specificity
Not applicable. This product is a small-molecule reagent, not a biological targeting agent or antibody. No antigen/epitope specificity, clone, isotype, or species reactivity applies.
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