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3-Pentanone
3-Pentanone
3-Pentanone
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3-Pentanone
Skeletal formula of 3-pentanone
Skeletal formula of 3-pentanone
Ball-and-stick model of 3-pentanone
Ball-and-stick model of 3-pentanone
Names
Preferred IUPAC name
Pentan-3-one
Other names
Diethyl ketone, diethylketone, 3-pentanone, dimethyl acetone, propione, DEK, metacetone, methacetone, ethyl ketone fraction
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.002.265 Edit this at Wikidata
EC Number
  • 202-490-3
RTECS number
  • SA8050000
UNII
UN number 1156
  • InChI=1S/C5H10O/c1-3-5(6)4-2/h3-4H2,1-2H3 checkY
    Key: FDPIMTJIUBPUKL-UHFFFAOYSA-N checkY
  • InChI=1/C5H10O/c1-3-5(6)4-2/h3-4H2,1-2H3
    Key: FDPIMTJIUBPUKL-UHFFFAOYAJ
  • O=C(CC)CC
Properties
C5H10O
Molar mass 86.134 g·mol−1
Appearance Colorless liquid[1]
Odor Acetone-like[2]
Density 0.81 g/cm3 at 20 °C[2]
Melting point −39 °C (−38 °F; 234 K)[2]
Boiling point 102 °C (216 °F; 375 K)[2]
35 g/L[2]
Vapor pressure 35 mmHg[1]
−58.14·10−6 cm3/mol
Hazards
GHS labelling:
GHS02: FlammableGHS07: Exclamation mark
Danger
H225, H335, H336
P210, P233, P240, P241, P242, P243, P261, P271, P280, P303+P361+P353, P304+P340, P312, P370+P378, P403+P233, P403+P235, P405, P501
Flash point 12.78 °C (55.00 °F; 285.93 K)
425 °C (797 °F; 698 K)
Explosive limits 1.6–6.4%[1]
NIOSH (US health exposure limits):
PEL (Permissible)
 none[1]
REL (Recommended)
 TWA 200 ppm (705 mg/m3)[1]
IDLH (Immediate danger)
 N.D.[1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
☒N verify (what is checkY☒N ?)

3-Pentanone (also known as diethyl ketone) is a simple, symmetrical dialkyl ketone. It is a colorless liquid ketone with an odor like that of acetone. It is soluble in about 25 parts water, but miscible with organic solvents.

Uses

[edit]

3-Pentanone is primarily used as starting material in chemical synthesis. A major application is in the industrial synthesis of vitamin E.[3][4] It has also been used in the synthesis of Oseltamivir (Tamiflu).

3-Pentanone itself finds some use as a specialty solvent in paint, although it is less common than butanone.

Syntheses

[edit]

Ketonic decarboxylation route

[edit]

3-Pentanone is produced by ketonic decarboxylation of propanoic acid using metal oxide catalysts:

2 CH3CH2CO2H → (CH3CH2)2CO + CO2 + H2O

in the laboratory, the reaction can be conducted in a tube furnace.[5]

Carbonylation route

[edit]

It can also be prepared by combining ethylene, CO, and H2.[4] When the reaction is catalyzed by dicobalt octacarbonyl, water can be used as a source of hydrogen. A proposed intermediate is the ethylene-propionyl species [CH3C(O)Co(CO)3(ethylene)] which undergoes a migratory insertion to form [CH3COCH2CH2Co(CO)3]. The required hydrogen arises from the water shift reaction. For details, see[6] If the water shift reaction is not operative, the reaction affords a polymer containing alternating carbon monoxide and ethylene units. Such aliphatic polyketones are more conventionally prepared using palladium catalysts.[7]

Safety

[edit]

The TLV value for 3-pentanone is 200 ppm (705 mg/m3).[4] 3-pentanone can be hazardous if it comes in contact with the skin or eyes, and can cause irritation of the skin and redness, watering, and itching of the eyes. This chemical can also cause nervous system or organ damage if ingested. Although considered stable, 3-pentanone is extremely flammable if exposed to flame, sparks, or another source of heat. For safety, it should be stored in a flammable materials cabinet away from heat or sources of ignition, preferably in a cool, well-ventilated area.[8]

See also

[edit]

References

[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

3-Pentanone

View on Grokipedia
from Grokipedia
3-Pentanone, also known as diethyl ketone or pentan-3-one, is a simple symmetrical aliphatic with the molecular formula C5H10O and the CH3CH2C(O)CH2CH3. This compound is a colorless, mobile with an acetone-like and a molecular weight of 86.13 g/mol. Key physical properties include a of 101.7 °C, a of -39 °C, a of 0.8098 g/cm³ at 25 °C, and of 47,000 mg/L in at 20 °C, while being miscible with and . Chemically, it is flammable with a of 13 °C and forms explosive mixtures with air, reacting vigorously with strong oxidizers. 3-Pentanone occurs naturally in various plants such as and , as well as in foods like , , and asparagus. It is primarily used as a starting material in , including the industrial production of , and as a in paints and other applications. Safety concerns include its high flammability and potential to irritate the eyes, , and , with occupational exposure limits set at 200 ppm (8-hour TWA) by OSHA and ACGIH.

Properties

Physical properties

3-Pentanone is a simple aliphatic with the molecular formula C₅H₁₀O and the CH₃CH₂C(O)CH₂CH₃. Its is 86.13 g/mol. It appears as a clear, colorless with an acetone-like . The of 3-pentanone is 0.81 g/cm³ at 20 °C. It has a of -39 °C and a of 102 °C at standard . The flash point is 13 °C (open cup). 3-Pentanone is miscible with most organic solvents and exhibits limited in , approximately 47 g/L at 20 °C. Its is 25.85 mmHg at 20 °C, and the is 1.3905 at 25 °C.
PropertyValueConditions
Density0.81 g/cm³20 °C
Melting point-39 °C-
Boiling point102 °C760 mmHg
Flash point13 °COpen cup
Water solubility47 g/L20 °C
Vapor pressure25.85 mmHg20 °C
Refractive index1.390525 °C (D line)

Chemical properties

3-Pentanone, also known as pentan-3-one, is a simple symmetrical dialkyl characterized by a (C=O) positioned at the third carbon in a five-carbon chain, with identical ethyl groups (CH₃CH₂-) flanking the carbonyl carbon, resulting in the molecular formula C₅H₁₀O and structure CH₃CH₂C(O)CH₂CH₃. This symmetry distinguishes it from unsymmetrical isomers like (CH₃C(O)CH₂CH₂CH₃), where the alkyl groups differ, affecting spectral simplicity and molecular behavior. The confers significant polarity to the molecule, with a dipole moment of 2.70 D arising from the electronegative oxygen atom. This polarity enables 3-pentanone to engage in dipole-dipole interactions and act as a acceptor through the lone pairs on oxygen, though it lacks hydrogen bond donors. Chemically, 3-pentanone remains relatively stable under neutral conditions but is reactive at the electrophilic carbonyl carbon, readily undergoing reactions typical of ketones. Additionally, the alpha-hydrogens on the adjacent methylene groups exhibit moderate acidity (pKₐ ≈ 20), facilitating enolization to form an or ion under basic conditions. In terms of spectroscopic properties, the infrared (IR) spectrum of 3-pentanone features a characteristic C=O stretching absorption at approximately 1715 cm⁻¹, indicative of the unconjugated ketone functionality. The ¹H NMR spectrum reflects the molecule's symmetry with two primary signals: a triplet at δ ≈ 1.0 ppm for the six equivalent methyl protons (CH₃) and a quartet at δ ≈ 2.4 ppm for the four equivalent methylene protons (CH₂), due to adjacent coupling. In ¹³C NMR, signals appear for the equivalent CH₃ and CH₂ carbons (around 8 ppm and 35 ppm, respectively) and the carbonyl carbon (around 208 ppm). Compared to 2-pentanone, which displays a more complex NMR pattern with four ¹H signals due to non-equivalent protons, the symmetry of 3-pentanone simplifies analysis; both isomers exhibit nearly identical boiling points of about 102 °C, underscoring the carbonyl's dominant influence on intermolecular forces over subtle structural symmetry effects.

Synthesis

Ketonic decarboxylation

Ketonic decarboxylation, also known as ketonization, represents the primary industrial method for synthesizing 3-pentanone from propanoic acid. In this process, two molecules of propanoic acid undergo thermal decomposition to form the symmetrical , releasing and as byproducts. The balanced reaction equation is: 2\ceCH3CH2CO2H−>(CH3CH2)2CO+CO2+H2O2 \ce{CH3CH2CO2H -> (CH3CH2)2CO + CO2 + H2O} This method is particularly suited for producing symmetrical ketones like 3-pentanone due to the straightforward coupling of identical alkyl chains. Historically, ketonic decarboxylation has been recognized as a classic approach for preparing symmetrical ketones from carboxylic acids, with early descriptions dating back to 1612 and more systematic modern accounts emerging in the late , such as W. H. Perkin's 1886 work on base-catalyzed of acids. The reaction's simplicity and reliance on abundant feedstocks have made it enduring, despite periodic rediscoveries by chemists over centuries. The mechanism involves the formation of a β-keto acid intermediate through of two molecules, followed by to yield the . This process is typically catalyzed by metal oxides such as CaO or MgO, which facilitate formation and C–C coupling at elevated temperatures of 300–400 °C. The vapor-phase reaction operates under moderate pressure (5–35 psi) with short contact times (3–5 seconds) to optimize selectivity. In industrial settings, this method achieves yields of 70–98% for 3-pentanone, depending on the catalyst system, with high selectivity (>95%) when using supported metal oxides like MnO₂ on alumina. Its efficiency stems from the low cost of propanoic acid, derived from inexpensive or sources, making it economically viable for bulk production. A common laboratory variation employs of , where the salt is heated to 400–500 °C, directly yielding 3-pentanone through without additional catalysts. This approach, while lower-yielding in small-scale setups, illustrates the reaction's versatility for symmetrical synthesis.

Carbonylation route

The carbonylation route provides an alternative industrial synthesis of 3-pentanone from , , and , contrasting with the ketonic method. The primary reaction is: 2\ceCH2=CH2+CO+H2−>(CH3CH2)2CO2 \ce{CH2=CH2 + CO + H2 -> (CH3CH2)2CO} A variant utilizes as the hydrogen source via the water-gas shift reaction: 2\ceCH2=CH2+2CO+H2O−>(CH3CH2)2CO+CO22 \ce{CH2=CH2 + 2 CO + H2O -> (CH3CH2)2CO + CO2} This process operates through a hydroformylation-like mechanism followed by hydrogenation, featuring intermediates such as the ethylene-propionyl species \ce{[CH3CH2C(O)Co(CO)3(ethylene)]}, which undergoes migratory insertion to form \ce{[CH3CH2C(O)CH2CH2Co(CO)3]}, ultimately yielding the ketone. The reaction is typically catalyzed by dicobalt octacarbonyl, \ce{Co2(CO)8}, under high-pressure conditions of 100–300 atm and temperatures ranging from 100–200 °C, enabling efficient conversion in a continuous flow setup. Ethylene feedstock is primarily obtained from the steam cracking of petrochemical sources such as naphtha or natural gas liquids. This route offers advantages in scalability for large-scale production, as it leverages abundant gaseous feedstocks and integrates seamlessly with existing olefin hydroformylation infrastructure in petrochemical plants. Modern variations, emerging prominently since the 1980s, incorporate rhodium-based catalysts, such as \ce{Rh/CeO2}, to enhance selectivity toward 3-pentanone while minimizing byproducts like propanal from competing hydroformylation pathways; as of 2023, these achieve >90% selectivity at 10–50 atm.

Uses

Solvent applications

3-Pentanone functions as a medium-volatility in the paints and coatings industry, where it is employed in formulations for lacquers and similar applications due to its ability to dissolve resins and provide controlled evaporation rates. Its solvency is derived from the of the group, enabling effective interaction with polar substrates like derivatives. In cleaning products, 3-pentanone is utilized in degreasers and extractants, leveraging its capacity to dissolve oils, resins, and other organic residues efficiently. This makes it suitable for industrial cleaning tasks requiring removal of greasy or resinous contaminants without excessive residue. finds minor application as an ethereal odorant in food additives and , where it imparts a subtle acetone-like scent in low concentrations; it is recognized by the FDA under UNII 9SLZ98M9NK for such uses. In niche settings, 3-pentanone has been explored experimentally since in huff-n-puff injection techniques for from tight reservoirs, showing potential to improve oil mobilization in fractured porous media. The solvent market accounts for the primary demand.

Synthetic intermediate

3-Pentanone serves as a key starting material in the synthesis of (Tamiflu), an antiviral medication for treatment, through routes involving protection steps and asymmetric transformations developed by in the . In one efficient formal synthesis from D-ribose, 3-pentanone is employed to form a ketal on the sugar, facilitating subsequent iodination and ring-opening reactions en route to the scaffold. This application highlights its utility in pharmaceutical production. In the industrial production of (), 3-pentanone acts as an intermediate in multi-step processes involving and cyclization to construct the chroman . This role underscores its importance in nutritional supplement manufacturing, leveraging its reactivity for high-yield transformations. Beyond pharmaceuticals and vitamins, 3-pentanone is utilized in synthesis as a precursor for intermediates, notably pendimethalin, a dinitroaniline compound effective against broadleaf weeds. In , it functions as a building block for fragrance precursors, imparting ethereal notes through derivatization into sulfur-containing or unsaturated ketones that enhance scent profiles in perfumes and . Common reactions exploiting 3-pentanone's include with Grignard reagents, such as , to yield tertiary alcohols like 3-ethyl-3-pentanol after . For chain extension, aldol condensations with aldehydes like under basic catalysis produce β-hydroxy ketones or α,β-unsaturated ketones, forming longer carbon frameworks with improved selectivity due to the ketone's steric bulk compared to acetone. This steric hindrance favors regioselective formation at the , making 3-pentanone preferable in reactions requiring control over multiple substitution sites.

Safety

Health effects

3-Pentanone primarily enters the body through of its vapors, which is the most common occupational exposure route, but it can also be absorbed via contact, eye exposure, or . Acute exposure to 3-pentanone irritates the eyes, causing redness and pain, and the , potentially leading to or dryness. may irritate the , resulting in coughing, , , , or , and high concentrations can cause drowsiness or . Oral is toxic, with an LD50 of approximately 2.14 g/kg in rats, indicating moderate . Chronic exposure to 3-pentanone may lead to defatting and dryness from repeated contact. The American Conference of Governmental Industrial Hygienists (ACGIH) has established a (TLV) of 200 ppm (705 mg/m³) as an 8-hour time-weighted average, with a of 300 ppm, to prevent upper irritation and impairment. 3-Pentanone is not classified as a by the International Agency for Research on Cancer (IARC Group 3: not classifiable as to its carcinogenicity to humans). In case of exposure, measures include flushing eyes or skin with plenty of water for at least and removing contaminated clothing; for inhalation, move the affected person to fresh air and provide rest, while ingestion requires immediate medical attention without inducing vomiting.

Flammability and handling

3-Pentanone is classified as a highly flammable liquid under the Globally Harmonized System (GHS) as Flammable Liquid Category 2, posing significant fire and hazards due to its low and ability to form mixtures with air. Its is 13 °C (open cup), meaning it can ignite at relatively low temperatures. The lower and upper limits in air are 1.6 vol% and 7.7 vol%, respectively, indicating the concentration range where vapors can ignite and propagate an . The is approximately 452 °C, above which the substance can spontaneously combust without an external ignition source. Safe handling requires storage in cool, well-ventilated areas separated from ignition sources, strong oxidizers, and other incompatible materials to prevent reactions or fires. Explosion-proof electrical equipment and non-sparking tools should be used during operations to minimize spark-induced ignition risks. Grounding and bonding containers during transfer can further reduce hazards. Vapors may cause mild respiratory irritation during handling, necessitating the use of appropriate in enclosed spaces. Under U.S. regulations, 3-pentanone is classified as a hazardous chemical per the (OSHA) Hazard Communication Standard (29 CFR 1910.1200), requiring labeling, safety data sheets, and worker training. For transportation, it is assigned 1156, Hazard Class 3 (flammable liquids), and Packing Group II, indicating moderate danger level for shipping by road, rail, air, or sea. In the event of a spill, the area should be evacuated, and the liquid absorbed using inert materials such as sand or ; the site must then be ventilated to disperse vapors while strictly avoiding open flames or sparks. As a (VOC), uncontrolled releases of 3-pentanone can contribute to tropospheric formation and , subject to emissions regulations under the Clean Air Act. It has low potential for and is not highly toxic to aquatic life.

References

  1. https://pubchem.ncbi.nlm.nih.gov/compound/3-Pentanone
  2. https://webbook.nist.gov/cgi/cbook.cgi?ID=C96220&Mask=200
  3. https://www.osha.gov/sites/default/files/methods/osha-pv2136.pdf
  4. https://www.spectrumchemical.com/3-pentanone-tci-p0061
  5. https://www.sigmaaldrich.com/US/en/product/sigald/127604
  6. https://pubchem.ncbi.nlm.nih.gov/compound/7288
  7. https://www.stenutz.eu/chem/solv6.php?name=3-pentanone
  8. https://www.chem.ucalgary.ca/courses/351/Carey5th/Ch21/ch21-2.html
  9. https://www2.chemistry.msu.edu/faculty/reusch/virttxtjml/spectrpy/infrared/irspec1.htm
  10. https://www.chem.purdue.edu/jmol/nmr/3pnone.html
  11. https://patents.google.com/patent/US4754074A/en
  12. https://chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/ejoc.200400546
  13. https://pubs.acs.org/doi/10.1021/ed081p1362
  14. https://www.sciencedirect.com/science/article/abs/pii/S0920586118316766
  15. https://www.chemicalbook.com/article/3-pentanone-uses-synthesis-and-hazards.htm
  16. https://patents.google.com/patent/US3059031A/en
  17. https://pubs.acs.org/doi/10.1021/acscatal.2c06123
  18. https://www.nbinno.com/?news/TDL-3-pentanone-properties-applications-and-uses
  19. https://www.thegoodscentscompany.com/data/rw1042361.html
  20. https://www.sciencedirect.com/science/article/abs/pii/S0920410522002625
  21. https://www.verifiedmarketreports.com/product/3-pentanone-market/
  22. https://pmc.ncbi.nlm.nih.gov/articles/PMC7382934/
  23. https://www.researchgate.net/publication/40032076_Efficient_Formal_Synthesis_of_Oseltamivir_Phosphate_Tamiflu_with_Inexpensive_D-Ribose_as_the_Starting_Material
  24. https://patents.google.com/patent/CN102701990A/en
  25. https://chem.libretexts.org/Bookshelves/Organic_Chemistry/Organic_Chemistry_%28OpenStax%29/17%253A_Alcohols_and_Phenols/17.05%253A_Alcohols_from_Carbonyl_Compounds_-_Grignard_Reagents
  26. https://www.masterorganicchemistry.com/2022/04/14/aldol-addition-and-condensation/
  27. https://pubs.acs.org/doi/10.1021/jo951485q
  28. https://www.inchem.org/documents/icsc/icsc/eics0874.htm
  29. https://monographs.iarc.who.int/list-of-classifications/
  30. https://chemicalsafety.ilo.org/dyn/icsc/showcard.display?p_card_id=0874
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