504-20-1

Basic information

• Product Name: 2,6-DIMETHYL-2,5-HEPTADIEN-4-ONE
• Synonyms: diisopropylidineacetone;Foron;Phoron;s-Diisopropylidene acetone;DIISOPROPYLIDENEACETONE;2,6-DIMETHYL-2,5-HEPTADIEN-4-ONE;2,6-DIMETHYL-2,5-HEPTADIENE-4-ONE;SYM-DIISOPROPYLIDENEACETONE
• CAS NO: 504-20-1
• Molecular Formula: C₉H₁₄O
• Molecular Weight: 138.21
• EINECS: 207-986-3
• Mol File: 504-20-1.mol
• Article Data: 18

Chemical Properties

• Melting Point: 23-26 °C(lit.)
• Boiling Point: 198-199 °C(lit.)
• Flash Point: 175 °F
• Appearance: /
• Density: 0.885 g/mL at 25 °C(lit.)
• Vapor Density: 4.8 (vs air)
• Vapor Pressure: 0.38 mm Hg ( 20 °C)
• Refractive Index: n20/D 1.497(lit.)
• Storage Temp.: 2-8°C
• Solubility: Chloroform (Slightly), Methanol (Slightly)
• Merck: 7333
• CAS DataBase Reference: 2,6-DIMETHYL-2,5-HEPTADIEN-4-ONE(CAS DataBase Reference)
• NIST Chemistry Reference: 2,6-DIMETHYL-2,5-HEPTADIEN-4-ONE(504-20-1)
• EPA Substance Registry System: 2,6-DIMETHYL-2,5-HEPTADIEN-4-ONE(504-20-1)

Safety Data

• Safety Statements: S22:Do not inhale dust.; S24/25:Avoid contact with skin and eyes.
• WGK Germany: 3
• RTECS: MI5500000
• Hazardous Substances Data: 504-20-1(Hazardous Substances Data)

Usage

Chemical Properties

Yellow liquid or yellow green prismatic crystal

Uses

Diisopropylidene Acetone is a reagent used in the preparation of biaryls by Suzuki-Miyaura cross coupling reaction.

General Description

A yellowish liquid with a solvent-like odor. Density 7.3 lb / gal. Very low vapor pressure (0.38 mm Hg at 68°F). Flash point 185°F. Combustible but difficult to ignite. Used as a solvent for lacquers and coatings.

Air & Water Reactions

Slightly soluble in water.

Reactivity Profile

Ketones, such as 2,6-DIMETHYL-2,5-HEPTADIEN-4-ONE, are reactive with many acids and bases liberating heat and flammable gases (e.g., H2). The amount of heat may be sufficient to start a fire in the unreacted portion of the ketone. Ketones react with reducing agents such as hydrides, alkali metals, and nitrides to produce flammable gas (H2) and heat. Ketones are incompatible with isocyanates, aldehydes, cyanides, peroxides, and anhydrides. They react violently with aldehydes, HNO3, HNO3 + H2O2, and HClO4.

Health Hazard

Inhalation or contact with material may irritate or burn skin and eyes. Fire may produce irritating, corrosive and/or toxic gases. Vapors may cause dizziness or suffocation. Runoff from fire control or dilution water may cause pollution.

Safety Profile

Moderately toxic by subcutaneous route. Combustible when exposed to heat or flame; can react with oxidizing materials. To fight fire, use foam, CO2, dry chemical. When heated to decomposition it emits acrid smoke and irritating fumes. See also ISOPHORON

Purification Methods

Crystallise phorone repeatedly from EtOH. [Beilstein 1 IV 3564.]

InChI:InChI=1/C9H14O/c1-7(2)5-9(10)6-8(3)4/h5-6H,1-4H3

Synthetic route

Phenyl vinyl ketone (768-03-6) → phorone (504-20-1) + isophorol (470-99-5)

Conditions	Yield
With aluminium tris(2,6-diphenylphenoxide); n-butyllithium; diisobutylaluminium hydride In toluene at -78 - 25℃; for 0.25h; Yields of byproduct given;	A 99% B n/a

1-benzyl-2,2,6,6-tetramethylpiperidine-4-one (52981-86-9) → phorone (504-20-1)

Conditions	Yield
With C20H29ClO2P2Pt In water; toluene at 105℃; for 5h; Reagent/catalyst;	90%

acetone (67-64-1) → 4-methyl-pent-3-en-2-one (141-79-7) + phorone (504-20-1) + 4-Hydroxy-4-methyl-2-pentanone (123-42-2)

Conditions	Yield
With titanium tetrachloride; NCNMe2 In benzene at 25℃;	A 82% B 2% C 8%
With sodium hydroxide In benzene at 40℃; Mechanism; Kinetics; benzyltriethylammonium chloride presence;
With sodium hydroxide; N-benzyl-N,N,N-triethylammonium chloride In benzene at 40℃; reaction order, effect of concentration on the initial rate;
With sodium hydroxide; N-benzyl-N,N,N-triethylammonium chloride In benzene at 40℃; Mechanism; effect concentrations, initial rate;
With MgO/ZrO2 mixed oxides at 249.84℃;

1,2,2,6,6-pentamethyl-4-piperidone methiodide (113308-50-2) → phorone (504-20-1)

Conditions	Yield
With potassium hydroxide In water for 1h;	55%

2,6-dimethyl-4-(1'-methyl-2'-propenyl)-1,6-heptadien-4-ol → phorone (504-20-1) + (E)-2,5-dimethyl-2,5-heptadien-4-one (115819-23-3) + 2,6-dimethyl-hepta-1,5-dien-4-one (5837-45-6) + (E)-2,5-dimethyl-1,5-heptadien-4-one

Conditions	Yield
With potassium hydride In N,N,N,N,N,N-hexamethylphosphoric triamide at 80℃;	A 20% B 4% C 47% D 8%

acetone (67-64-1) → phorone (504-20-1) + di-i-propyl peroxide (16642-57-2)

Conditions	Yield
With sodium In tetrahydrofuran Ambient temperature; Reductive dimerization, other metal, using irradiation;	A n/a B 10%

2,6-dimethyl-4-(2'-propenyl)-1,6-heptadien-4-ol (81925-78-2) → phorone (504-20-1) + 6-methyl-hepta-1,5-dien-4-one (33698-67-8) + 2,6-dimethyl-hepta-1,5-dien-4-one (5837-45-6) + (5E)-2-methyl-1,5-heptadien-4-one (115818-79-6)

Conditions	Yield
With potassium hydride In N,N,N,N,N,N-hexamethylphosphoric triamide at 80℃; Yield given;	A n/a B 1% C n/a D 4%

6-hydroxy-2,6-dimethyl-hept-2-en-4-one (5857-71-6) → 3,5,5-Trimethylcyclohex-2-en-1-one (78-59-1) + phorone (504-20-1)

Conditions	Yield
beim Erhitzen unter gewoehnlichem Druck;

6-hydroxy-2,6-dimethyl-hept-2-en-4-one (5857-71-6) → phorone (504-20-1)

Conditions	Yield
With sulfuric acid at 80℃;

3,5-dibromo-2,6-dimethylhepta-2,5-dien-4-one (5682-79-1) → phorone (504-20-1) + 3-methyl-1-[4,4,5,5-tetramethyl-2-(2-methyl-propenyl)-cyclopent-1-enyl]-but-2-en-1-one (71500-18-0)

Conditions	Yield
With hydrogenchloride; amalgamated zinc

2,6-dihydroxy-2,6-dimethyl-heptan-4-one (3682-91-5) → 2,2,6,6-tetramethyltetrahydropyran-4-one (1197-66-6) + phorone (504-20-1)

Conditions	Yield
With sulfuric acid Nebenprod. 2: 6-Hydroxy-2,6-dimethyl-hept-2-en-4-on;

2,6-dihydroxy-2,6-dimethyl-heptan-4-one (3682-91-5) → phorone (504-20-1)

2,6-dihydroxy-2,6-dimethyl-heptan-4-one (3682-91-5) → phorone (504-20-1) + 6-hydroxy-2,6-dimethyl-hept-2-en-4-one (5857-71-6)

Conditions	Yield
With sulfuric acid

2,6-dihydroxy-2,6-dimethyl-heptan-4-one (3682-91-5) + oxalic acid (144-62-7) → phorone (504-20-1)

2,6-dihydroxy-2,6-dimethyl-heptan-4-one (3682-91-5) + acetic anhydride (108-24-7) → phorone (504-20-1)

acetyl chloride (75-36-5) + acetone (67-64-1) → 4-methyl-pent-3-en-2-one (141-79-7) + phorone (504-20-1)

Conditions	Yield
With zinc(II) chloride beim Behandeln des Reaktionsproduktes mit Wasserdampf und Erhitzen des Destillats mit ueberschuessiger alkoh.Kalilauge waehrend einiger Minuten bis nahe zum Sieden;
With zinc(II) chloride beim Bahandeln des Reaktionsproduktes mit Wasserdampf und Erhitzen des Destillats mit ueberschuessiger alkoh. Kalilauge waehrend einiger Minuten bis nahe zum Sieden;
With zinc(II) chloride Behandeln der Reaktionsproduktes mit Wasserdampf und Erhitzen des Destillats mit ueberschuessiger alkoh.Kalilauge waehrend einiger Minuten bis nahe zum Sieden;

isopropyl alcohol (67-63-0) → phorone (504-20-1)

Conditions	Yield
With zinc(II) sulfate at 380 - 400℃;

t-butyl bromide (507-19-7) + acetone (67-64-1) → 4-methyl-pent-3-en-2-one (141-79-7) + phorone (504-20-1)

acetone (67-64-1) + tert-butyl alcohol (75-65-0) → 4-methyl-pent-3-en-2-one (141-79-7) + phorone (504-20-1)

Conditions	Yield
With hydrogen bromide

aluminum tri-tert-butoxide (556-91-2) + acetone (67-64-1) + benzene (71-43-2) → 4-methyl-pent-3-en-2-one (141-79-7) + phorone (504-20-1)

acetone (67-64-1) → 4-methyl-pent-3-en-2-one (141-79-7) + phorone (504-20-1)

acetone (67-64-1) → phorone (504-20-1)

Conditions	Yield
With phosphoric acid at 150℃;
With phosphoric acid
With hydrogenchloride; aluminium trichloride

acetone (67-64-1) → phorone (504-20-1) + propanone 1-oxime (306-44-5)

Conditions	Yield
With nitrosylchloride

3,3-Dimethylacryloyl chloride (3350-78-5) + isobutene (115-11-7) → phorone (504-20-1)

Conditions	Yield
With tin(IV) chloride

4-methyl-6-(2-methylprop-1-en-1-yl)-2H-pyran-2-one (4394-72-3) → phorone (504-20-1)

Conditions	Yield
(i) NaOH, MeOH, (ii) (heating); Multistep reaction;

2,2-diethoxypropane (126-84-1) → phorone (504-20-1)

Conditions	Yield
(i) PhNHMe, TsOH, (ii) aq. HCl; Multistep reaction;

4-benzyl-2,6-dimethyl-1,6-heptadien-4-ol (81925-77-1) → phorone (504-20-1) + 2,6-dimethyl-hepta-1,5-dien-4-one (5837-45-6)

Conditions	Yield
With potassium hydride In N,N,N,N,N,N-hexamethylphosphoric triamide at 40℃; Yield given. Yields of byproduct given;

acetone (67-64-1) → methanol (67-56-1) + 4-methyl-pent-3-en-2-one (141-79-7) + phorone (504-20-1) + 4-Hydroxy-4-methyl-2-pentanone (123-42-2)

Conditions	Yield
at 350.1℃; under 78681.3 Torr; for 0.138889h; Product distribution; var. temp.;

acetone (67-64-1) → 3,5,5-Trimethylcyclohex-2-en-1-one (78-59-1) + 4-methyl-pent-3-en-2-one (141-79-7) + phorone (504-20-1) + carbon dioxide (124-38-9) + carbon monoxide (201230-82-2) + isobutene (115-11-7)

Conditions	Yield
With zeolite HY at 350℃; Product distribution; effect of acidity on the conversion of acetone over AlPO4-5, SAPO-5 phosphates and modifiedY zeolites;

2,5,5-trimethyl-4-(2'-methyl-2'-propenyl)-1,6-heptadien-4-ol → phorone (504-20-1) + 2,6-dimethyl-hepta-1,5-dien-4-one (5837-45-6)

Conditions	Yield
With potassium hydride In N,N,N,N,N,N-hexamethylphosphoric triamide at 40℃; Yield given. Yields of byproduct given;

phorone (504-20-1) → 2,2,6,6-Tetramethyl-4-piperidone (826-36-8)

Conditions	Yield
With ammonium hydroxide at -80 - 85℃;	98%
With ammonia; water
With ammonia
With ammonium hydroxide; sodium hydroxide 1.) 25 deg C, 3 days, 80 deg C, 60 min; 2.) 0-5 deg C; Yield given. Multistep reaction;
With ammonium hydroxide In water at 55 - 85℃;

phorone (504-20-1) → 3,3,3',3'-tetramethyl-5,5'-spirodiisoxazolidine

Conditions	Yield
With hydroxylamine hydrochloride; sodium methylate In methanol for 6h; Heating;	95%

phorone (504-20-1) + 1,2-diphosphinoethane (5518-62-7) → 1,2-bis(2,2,6,6-tetramethyl-phosphinan-4-on)ethane

Conditions	Yield
at 120℃; for 20h;	93%
at 120℃; for 20h;	93%

phorone (504-20-1) + allyl bromide (106-95-6) → (+/-)-2-(3''-butenyl)-1,1-bis[1'-(2'methyl)propenyl]cyclopropane

Conditions	Yield
Stage #1: allyl bromide With indium In tetrahydrofuran for 1.5h; Metallation; Stage #2: phorone In tetrahydrofuran Addition; Stage #3: With hydrogenchloride; oxygen; lithium bromide In tetrahydrofuran; diethyl ether Substitution; cyclization; Further stages.;	92%
Yield given. Multistep reaction;

phorone (504-20-1) → diisobutyl ketone (108-83-8)

Conditions	Yield
With ethanol; lithium; nickel dichloride In tetrahydrofuran at 20℃; for 12h;	91%
With triethylsilane; ethanol; palladium dichloride for 6h; Heating;	90%
With formic acid; (η5-C4Ph4COHOC4Ph4-η5)(μ-H)(CO)4Ru2 at 100℃; for 1.2h;	88%

phorone (504-20-1) → <15N>-2,2,6,6-tetramethyl-4-piperidone (137003-52-2)

Conditions	Yield
With aq. (15N)ammonia at -80 - 85℃;	91%
With sodium hydroxide; disodium hydrogenphosphate; 15N-ammonium sulfate In benzene at 95℃; for 240h;	86%
With sodium hydroxide In benzene at 90℃; for 240h; double Michael addition;	66%

phorone (504-20-1) + triphenyl bismuth (2+); dichloride (507233-69-4, 594-30-9, 28719-54-2) → 2,6-dimethyl-3-phenylhept-1,5-dien-4-one

Conditions	Yield
With N,N,N,N,N,N-hexamethylphosphoric triamide; lithium diisopropyl amide In tetrahydrofuran; n-heptane; ethylbenzene at -78 - 20℃; for 2h; Arylation;	89%

dicyano-bis-(1,10-phenanthroline)-iron(II) dihydrate (15362-08-0) + phorone (504-20-1) → cis-bis(6-isocyano-2,6-dimethyl-2-hepten-4-one)bis(1,10-phenanthroline)iron(II)-bis(tetrafluoroborate) (123623-97-2)

Conditions	Yield
With Et2O-HBF4 In ethanol dropwise addn. of phorone to a soln. of 54% Et2O-HBF4 and Fe-compd. at room temp., a suspn. develops after 20 min., pptn. on stirring for 20 h; centrifugating, repeated recrystn. (CH2Cl2/ether), washing 3 times with ether and pentane, drying in vac., elem. anal.;	89%

phorone (504-20-1) + (2′,4′,6′-triisopropyl-3,6-dimethoxybiphenyl-2-yl)phosphine → 2,2,6,6-tetramethyl-1-(2′,4′,6′-triisopropyl-3,6-dimethoxybiphenyl-2-yl)phosphinan-4-one

Conditions	Yield
With 1,1,1,3',3',3'-hexafluoro-propanol at 50℃; Michael Addition;	88%
at 160℃; for 22h; Inert atmosphere;	66%
Heating;

phorone (504-20-1) → 2,3,5,6-tetrabromo-2,6-dimethyl-heptan-4-one (73806-71-0)

Conditions	Yield
With bromine In tetrachloromethane for 0.5h; Ambient temperature;	86%
With carbon disulfide; bromine

phorone (504-20-1) → 3-isobutenyl-5,5-dimethyl-2-isoxazoline

Conditions	Yield
With hydroxylamine hydrochloride; sodium methylate In methanol for 6h; Heating;	85%

phorone (504-20-1) + recorcinol (108-46-3) → 4,4,4′,4′-tetramethyl-2,2′-spirobi[chroman]-7,7′-diol (3127-14-8)

Conditions	Yield
With hydrogenchloride In diethyl ether; dichloromethane for 24h; Heating;	85%

1,2-bis(phosphinomethyl)ferrocene (478658-93-4) + phorone (504-20-1) → 1,2-bis-(P-(2,2,6,6,-tetramethylphosphinan-4-one))dimethylferrocene

Conditions	Yield
at 120℃; for 20h; Inert atmosphere;	85%

N,N-dichloro-p-toluenesulfonamide (473-34-7) + propyl cyanide (109-74-0) + phorone (504-20-1) → 1-[2-(1-chloro-propyl)-5,5-dimethyl-3-(toluene-4-sulfonyl)-4,5-dihydro-3H-imidazol-4-yl]-3-methyl-but-2-en-1-one

Conditions	Yield
With 4 A molecular sieve at 20℃; for 8h;	81%

N,N-dichloro-p-toluenesulfonamide (473-34-7) + phorone (504-20-1) + acetonitrile (75-05-8) → 1-[2-dichloromethyl-5,5-dimethyl-3-(toluene-4-sulfonyl)-4,5-dihydro-3H-imidazol-4-yl]-3-methyl-but-2-en-1-one

Conditions	Yield
With 4 A molecular sieve at 20℃; for 8h;	81%

phorone (504-20-1) + ethylamine (75-04-7) → 6-ethylamino-2,6-dimethylhept-2-en-4-one (1392008-77-3)

Conditions	Yield
In water at 20℃; for 48h;	80%

phorone (504-20-1) + 2,6-dimethylphenyl isonitrile (119072-54-7, 2769-71-3) → 2,6-dimethyl-N-(3,3-dimethyl-5-(2-methyl-1-propenyl)-2(3H)-furanylidene)-benzenamine

Conditions	Yield
With gallium(III) trichloride In toluene at 100℃; for 12h;	78%

phorone (504-20-1) + Methyltriphenylphosphonium bromide (1779-49-3) → 2,6-dimethyl-4-methylene-2,5-heptadiene (927-02-6)

Conditions	Yield
Stage #1: Methyltriphenylphosphonium bromide With phenyllithium In diethyl ether; cyclohexane for 0.5h; Stage #2: phorone In diethyl ether; cyclohexane for 0.5h;	77%

phorone (504-20-1) → 3-chloro-2,6-dimethyl-1,5-heptadien-4-one (81454-78-6)

Conditions	Yield
With calcium hypochlorite; Methamphetamin In dichloromethane; water for 3h;	76%
With calcium hypochlorite In water	74%

phorone (504-20-1) → 2,2,6,6-tetramethyltetrahydro-1-selenapyran-4-one (132132-58-2)

Conditions	Yield
With aluminum selenide; sodium acetate In ethanol at 75 - 78℃; for 6h;	74.5%

N,N-dichloro-p-toluenesulfonamide (473-34-7) + phorone (504-20-1) + propiononitrile (107-12-0) → 1-[2-(1-chloro-ethyl)-5,5-dimethyl-3-(toluene-4-sulfonyl)-4,5-dihydro-3H-imidazol-4-yl]-3-methyl-but-2-en-1-one

Conditions	Yield
With 4 A molecular sieve at 20℃; for 8h;	74%

Isobutyronitrile (78-82-0) + phorone (504-20-1) + toluene-4-sulfonamide (70-55-3) → 1-[2-isopropyl-5,5-dimethyl-3-(toluene-4-sulfonyl)-4,5-dihydro-3H-imidazol-4-yl]-3-methyl-but-2-en-1-one

Conditions	Yield
With N-chloro-succinimide; molecular sieve In acetonitrile at 50℃; for 60h;	74%

phorone (504-20-1) + N,N-dichloro-2-nitrobenzenesulfonamide (52187-72-1) + acetonitrile (75-05-8) → 1-(2-dichloromethyl-3-(2-nitrobenzenesulfonyl)-5,5-dimethyl-4,5-dihydro-3H-imidazol-4-yl)-3-methyl-but-2-en-1-one

Conditions	Yield
With N-chloro-succinimide at 50℃; for 60h;	74%

phorone (504-20-1) + cyclopenta-1,3-diene (542-92-7) → 6,6-Bis(2-methyl-1-propenyl)fulvene

Conditions	Yield
With sodium hydroxide In methanol at 60℃; for 2h;	73%

phorone (504-20-1) + phenylphosphane (638-21-1) → 1-phenyl-2,2,6,6-tetramethyl-4-phosphorinanone (13887-05-3)

Conditions	Yield
at 120℃; for 6h;	72.5%
at 120℃; for 21h;	58%
at 150℃; for 15h; Inert atmosphere;	47%
(i) NaOMe, EtOH, (ii) AcOH; Multistep reaction;
at 115 - 130℃;

phorone (504-20-1) → 4-AMINO-2,2,6,6-TETRAMETHYLPIPERIDINE (36768-62-4)

Conditions	Yield
With ammonia; acetic acid In methanol	71%
With acetic acid In methanol	64%
With ammonia; acetic acid In methanol	54%
With ammonia; acetic acid In methanol	41.5%
With acetic acid In methanol	38%

phorone (504-20-1) + toluene-4-sulfonamide (70-55-3) + acetonitrile (75-05-8) → 1-[2-dichloromethyl-5,5-dimethyl-3-(toluene-4-sulfonyl)-4,5-dihydro-3H-imidazol-4-yl]-3-methyl-but-2-en-1-one

Conditions	Yield
With N-chloro-succinimide; molecular sieve at 50℃; for 48h;	70%

Upstream product

• 640-01-7 1-nitroso-2,2,6,6-tetramethyl-4-piperidone 
• 3682-91-5 2,6-dihydroxy-2,6-dimethyl-heptan-4-one 
• 108-24-7 acetic anhydride 
• 144-62-7 oxalic acid 
• 5682-79-1 3,5-dibromo-2,6-dimethylhepta-2,5-dien-4-one 
• 5857-71-6 6-hydroxy-2,6-dimethyl-hept-2-en-4-one 
• 52185-71-4 1-benzyl-4-hydroxy-2,2,6,6-tetramethylpiperidine 
• 5554-54-1 1,2,2,6,6-pentamethyl-4-piperidone 
• 2403-89-6 1,2,2,6,6-pentamethyl-piperidin-4-ol 

Downstream Products

• 21454-58-0 Phoron-2.4-dinitro-phenylhydrazon (Bis-<2-Methyl-propenyl>-keton-2.4-dinitro-phenylhydrazon) 
• 77-08-7 3,3,3',3'-tetramethyl-2,3,2',3'-tetrahydro-[1,1']spirobiindene-5,6,5',6'-tetraol 
• 95-63-6 1,2,4-Trimethylbenzene 
• 108-67-8 1,3,5-trimethyl-benzene 
• 66622-42-2 2,6-dimethyl-2,6-diphenylheptan-4-one 
• 73806-71-0 2,3,5,6-tetrabromo-2,6-dimethyl-heptan-4-one 
• 108-83-8 diisobutyl ketone 
• 108-82-7 2,6-dimethyl-4-heptanol 
• 541-47-9 3-Methylbutenoic acid 
• 22842-41-7 2,2,6,6-tetramethyltetrahydro-4H-thiopyran-4-one 
• 1197-66-6 2,2,6,6-tetramethyltetrahydropyran-4-one 
• 826-36-8 2,2,6,6-Tetramethyl-4-piperidone 
• 2516-70-3 2,6-dimethyl-4-phenyl-hepta-2,5-dien-4-ol 
• 1483-64-3 1,1,4,4-tetraphenyl-butane 

Relevant articles and documents

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In-situ IR Spectroscopy Study of Reactions of C3 Oxygenates on Heteroatom (Sn, Mo, and W) doped BEA Zeolites and the Effect of Co-adsorbed Water

The reactions of acetone and hydroxyacetone over heteroatom doped BEA zeolites (Sn, Mo, and W) in the presence and absence of H2O vapor are investigated using infrared spectroscopy. Acetone is converted to mesityl oxide over Sn-BEA exclusively. At higher temperatures, larger oxygenates such as phorones, aromatics, and coke form. The presence of co-adsorbed water in Sn-BEA suppresses tautomerization. H2O vapor is also beneficial for minimizing coke formation at high temperatures. Hydroxyacetone is converted into 2-hydroxypropanal over Sn-BEA, exhibiting high affinity to Sn sites up to 400 °C. Sn-BEA catalyzes conversion of hydroxyacetone into the enol in the absence of H2O, but exposure to H2O induces the formation of 2-hydroxypropanal and subsequent conversion to acrolein. The Lewis acid descriptors are used to rationalize the reaction pathways. For the isomerization of hydroxyacetone into 2-hydroxypropanal, the hardness of acid sites influences the reaction and correlates with the overall Lewis acidity of the catalysts, respectively. However, the size of the exchanged metal significantly affects aldol condensation, where keto and enol forms of acetone adsorb to active sites simultaneously.

Aldol Condensation Versus Superbase-Catalyzed Addition of Ketones to Acetylenes: A Quantum-Chemical and Experimental Study

The mechanism of aldol condensation of ketones in KOH/DMSO superbasic media has been investigated using the B2PLYP(D2)/6-311+G**//B3LYP/6-31+G? quantum-chemical approach. It is found that the interaction of three ketone molecules resulting in the formation of the cyclohex-2-enone structure [isophorone or 3,5-dicyclohexyl-5-methylspiro(5.5)undec-2-en-1-one] is thermodynamically more favorable than the interaction of two, three, or four molecules of ketone, resulting in the formation of linear products of the condensation. The formation of the condensation products with the isophorone skeleton can significantly hinder the cascade reactions of ketones with acetylenes [to afford 6,8-dioxabicyclo(3.2.1)octanes or acylcyclopentenols] promoted by superbases. In particular, the kinetically more preferable reactions of autovinylation of 2-methyl-3-butyn-2-ol and autocondensation of acetone are the reasons why interaction of acetone with acetylene does not lead to the products of the cascade assemblies. The predominant formation of the products of these side reactions is confirmed experimentally.