2-methyltetrahydrofuran

Structural formula
Structural formula without stereochemistry
General
Surname	2-methyltetrahydrofuran
other names	Methyl tetrahydrofuran Tetrahydro-2-methylfuran
Molecular formula	C 5 H 10 O
Brief description	colorless liquid with an ethereal odor
External identifiers / databases
CAS number 96-47-9 ( racemate ) 63798-12-9 [( S ) - (+) - enantiomer] 63798-13-0 [( R ) - (-) - enantiomer] EC number 202-507-4 ECHA InfoCard 100.002.281 PubChem 7301 ChemSpider 7028 Wikidata Q209444
properties
Molar mass	86.13 g mol −1
Physical state	liquid
density	0.85 g cm −3 (racemate)
Melting point	−136 ° C (racemate)
boiling point	80 ° C (racemate)
Vapor pressure	136 h Pa (20 ° C) (racemate) 345 hPa (50 ° C) (racemate) 595 hPa (65 ° C) (racemate)
solubility	easily in water (140 g l −1 at 20 ° C) (racemate)
Refractive index	1.4059 (21 ° C)
safety instructions
GHS labeling of hazardous substances danger H and P phrases H: 225-302-315-318 EUH: 019 P: 210-280-301 + 312 + 330-305 + 351 + 338 + 310-370 + 378-403 + 235
Toxicological data	4500 mg kg −3 ( LD 50 ,  rabbit ,  transdermal )
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . Refractive index: Na-D line , 20 ° C

2-Methyltetrahydrofuran (2-MTHF) is an organic solvent and belongs to the class of cyclic ethers .

Extraction and presentation

2-methyltetrahydrofuran is a by-product of the industrial production of furfuryl alcohol from furfural . It can also be produced by a nickel- catalyzed hydrogenation of 2-methylfuran . This can be obtained from the furfural, which is accessible by processing plant pentoses , so that the production of 2-methyltetrahydrofuran can take place entirely from renewable raw materials.

A more recent process involves the cyclization and hydrogenation of levulinic acid , which can also be obtained from carbohydrates . All commercial manufacturing processes result in the racemate. A separation of enantiomers may chromatography on chiral stationary phases with supercritical media take place. The synthesis of ( S ) - (+) - 2-methyltetrahydrofuran is achieved through the hydrogenation of 2-methylfuran using chiral rhodium complex catalysts.

properties

Stereochemistry

The compound contains a stereocenter and can therefore occur in the form of two enantiomers . However, only the racemate is of practical importance .

( R ) -enantiomer (left), ( S ) -enantiomer (right)

Physical Properties

2-Methyltetrahydrofuran is a colorless, low-viscosity liquid with a characteristic odor. The boiling point at normal pressure is 80.3 ° C. According to Antoine, the vapor pressure function results from log ₁₀ (P) = A− (B / (T + C)) (P in kPa, T in ° C) with A = 5.95009, B = 1175.51 and C = 217.80 . The following table gives an overview of important thermodynamic properties.

Compilation of the most important thermodynamic properties

property	Type	Value [unit]	Remarks
Heat capacity	c p	156.89 J mol −1 K −1 (25 ° C) 1.82 J g −1 K −1 (25 ° C)
Critical temperature	T c	537 K
Critical pressure	p c	37.6763 bar
Critical volume	V c	0.267 l mol −1
Critical density	ρ c	0.3226 g ml −1
Acentric factor	ω c	0.300
Enthalpy of evaporation	Δ V H 0 Δ V H	34.0 kJ mol −1 30.43 kJ mol −1	at boiling point

The temperature dependence of the evaporation enthalpy can be calculated according to the simplified Watson equation Δ _V H = A · (1 − T _r ) ⁿ (Δ _V H in kJ / mol, T _r = (T / T _c ) reduced temperature) with A = 45.7503 Describe kJ / mol, n = 0.38 and T _c = 537.0 K in the temperature range between 136 K and 537 K.

With a water content of 10.6% by mass of the compound forms a boiling at 71 ° C azeotrope . Further azeotropic boiling mixtures are formed with methanol , ethanol , 1-propanol and 2-propanol .

Azeotropes with various solvents
solvent		Methanol	Ethanol	1-propanol	2-propanol	water
Methyltetrahydrofuran content	in%	43	66	99	82	89.4
boiling point	in ° C	62.8	74.4	79.5	77	71

At 20 ° C., 14 g of methyltetrahydrofuran dissolve in 100 g of water, and conversely, 4 g of water dissolve in 100 g of methyltetrahydrofuran. The solubility of water in 2-methyltetrahydrofuran changes only slightly with increasing temperature. In contrast, the solubility of methyltetrahydrofuran in water decreases with increasing temperature.

Solubilities in the system 2-methyltetrahydrofuran - water
temperature	in ° C	0.0	9.5	19.3	29.5	39.6	50.1	60.7	70.6
Solubility of water in methyltetrahydrofuran	in%	4.0	4.1	4.1	4.2	4.3	4.4	4.6	5.0
Solubility of methyltetrahydrofuran in water	in%	21.0	17.8	14.4	11.4	9.2	7.8	6.6	6.0

Safety-related parameters

2-methyltetrahydrofuran forms highly flammable vapor-air mixtures. The compound has a flash point below −12 ° C. The explosion range is between 1.5 vol.% As the lower explosion limit (LEL) and 8.9 vol.% As the upper explosion limit (UEL). A correlation of the explosion limits with the vapor pressure function results in a lower explosion point of −15 ° C and an upper explosion point of 18 ° C. The limit oxygen concentration at 100 ° C is 9.4 vol%. The ignition temperature is 270 ° C. The substance therefore falls into temperature class T3.

Chemical properties

Like many other ethers, 2-methyltetrahydrofuran tends to form peroxides in the presence of air . The rate of peroxide formation is similar to that of tetrahydrofuran. The commercial product contains butylated hydroxytoluene as a stabilizer. It is much more stable to acids than tetrahydrofuran.

use

2-Methyltetrahydrofuran is seen as a solvent alternative to tetrahydrofuran, especially in organometallic reactions. On the one hand, it has a low viscosity of 1.85 cp even at low temperatures such as −70 ° C , and on the other hand, the temperature range up to the higher boiling point of 80 ° C can be used. Since the compound solidifies like glass when it cools below the melting point , it can be used as a solvent for spectroscopic investigations at −196 ° C. Use as a by-product in motor gasoline has been successfully tested in the USA. In organic chemistry it is used as a reactant for the production of N -substituted 2-methylpyrrolidines.

Individual evidence

1. ↑ ^{a b c d e f g h i j k} Entry on tetrahydro-2-methylfuran in the GESTIS substance database of the IFA , accessed on January 15, 2020(JavaScript required) .
2. ↑ ^{a b c d e f g h} Aycock, DF: Solvent Applications of 2-Methyltetrahydrofuran in Organometallic and Biphasic Reactions in Org Process Res Dev . 11 (2007) 156-159, doi: 10.1021 / op060155c
3. ↑ David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Physical Constants of Organic Compounds, pp. 3-376.
4. ↑ Data sheet 2-methyltetrahydrofuran, anhydrous, ≥ 99%, inhibitor-free from Sigma-Aldrich , accessed on April 8, 2012 ( PDF ).
5. ↑ ^{a b c} Hoydonckx, HE; van Rhijn, VM; van Rhijn, W .; de Vos, DE Jacobs, PA: Furfural and Derivatives in Ullmanns Encyclopedia of Industrial Chemistry , 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, doi : 10.1002 / 14356007.a12_119.pub2 .
6. ↑ Lichtenthaler, FW: Carbohydrates as Organic Raw Materials in Ullmanns Encyclopedia of Industrial Chemistry, 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, doi : 10.1002 / 14356007.n05_n07 .
7. ↑ Schurig, V .; Schmalzing, D .; Schleimer, M .: Enantiomer separation on immobilized Chirasil metal and Chirasil Dex by gas chromatography and chromatography with supercritical gases in Angew. Chem. 103 (1991) 994-996, doi: 10.1002 / anie.19911030822 .
8. ↑ Schurig, V .; Buerkle, W .: Extending the scope of enantiomer resolution by complexation gas chromatography in J. Am. Chem. Soc. 104 (1982) 7573-7580, doi: 10.1021 / ja00390a031 .
9. ↑ Hey, Man; Zhou, Da-Qing; Ge, Hong-Li; Huang, Mei-Yu; Jiang, Ying-Yan: Catalytic Behavior of Wool-Rh Complex in Asymmetric Hydrogenation of 2-Methyl Furan in Polymer Adv. Techn. 14 (2003) 273-277, doi: 10.1002 / pat . 305 .
10. ↑ S. Rodrı́guez, H. Artigas, C. Lafuente, AM Mainar, F. M Royo: Isobaric vapor – liquid equilibrium of binary mixtures of some cyclic ethers with chlorocyclohexane at 40.0 and 101.3 kPa . In: Thermochimica Acta . tape 362 , no. 1-2 , 2000, pp. 153-160 , doi : 10.1016 / S0040-6031 (00) 00580-3 .
11. ↑ ^{a b c} V. K. Rattan, BK Gill, S. Kapoor: Isobaric Vapor-Liquid Equilibrium Data for Binary Mixture of 2-Methyltetrahydrofuran and Cumene . In: International Journal of Chemical and Molecular Engineering . tape 2 , no. 11 . World Academy of Science, Engineering and Technology , 2008, p. 41-44 ( waset.org ).
12. ↑ ^{a b} Rodriguez, R .; Lafuente, C .; Artigas, H .; Royo, FM; Urieta, JS: Thermodynamic Densities, speeds of sound, and isentropic compressibilities of a cyclic ether with chlorocyclohexane, or bromocyclohexane at the temperatures 298.15K and 313.15K in J. Chem. Thermodyn. 31 (1999) 139-149, doi: 10.1006 / jcht.1998.0437 .
13. ↑ ^{a b c} Kobe, KA; Ravicz, AE; Vohra, SP: Critical Properties and Vapor Pressures of Some Ethers and Heterocyclic Compounds in J. Chem. Eng. Data 1 (1956) 50-56, doi: 10.1021 / i460001a010 .
14. ^ ^{A b c d e} Carl L. Yaws, Prasad K. Narasimhan: Thermophysical Properties of Chemicals and Hydrocarbons - Chapter 1: Critical Properties and Acentric Factor, Organic Compounds , 1st Edition Elsevier 2008, ISBN 978-0-8155-1596-8 , P. 18, doi: 10.1016 / B978-081551596-8.50006-7 .
15. ↑ Stephenson, RM; Malanowski, S .: Handbook of the Thermodynamics of Organic Compounds , 1987, doi: 10.1007 / 978-94-009-3173-2 .
16. ^ ^{A b} Carl L. Yaws, Marco A. Satyro: Thermophysical Properties of Chemicals and Hydrocarbons - Chapter 7: Enthalpy of Vaporation, Organic Compounds , 1st Edition Elsevier 2008, ISBN 978-0-8155-1596-8 , p. 325, doi: 10.1016 / B978-081551596-8.50012-2 .
17. ↑ ^{a b c d} data sheet from PENN Specialty Chemicals, Inc., pdf ( Memento of the original from March 4, 2016 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. . 
18. ↑ RM Stephenson: Mutual Solubilities: Water-Ketones, Water-Ethers, and Water-Gasoline-Alcohols in J. Chem. Eng. Data 37 (1992) 80-95, doi: 10.1021 / je00005a024 .
19. ^ E. Brandes, W. Möller: Safety-related parameters - Volume 1: Flammable liquids and gases , Wirtschaftsverlag NW - Verlag für neue Wissenschaft GmbH, Bremerhaven 2003.
20. ↑ ^{a b} Watanabe, K .; Yamagiwa, N .; Torisawa, Y .: Cyclopentyl Methyl Ether as a New and Alternative Process Solvent in Org. Process Res. Dev. 11 (2007) 251-258, doi: 10.1021 / op0680136
21. ^ Osterberg, PM; Niemeier JK; Welch, CJ; Hawkins, JM; Martinelli, JR; Johnson, TE; Root, TW; Stahl, SS: Experimental Limiting Oxygen Concentrations for Nine Organic Solvents at Temperatures and Pressures Relevant to Aerobic Oxidations in the Pharmaceutical Industry in Org. Process Res. Dev. 19 (2015) 1537–1542, doi: 10.1021 / op500328f
22. ↑ Nicholls, D .; Sutphen, C .; Szware, M: Dissociation of lithium and sodium salts in ethereal solvents in J. Phys. Chem. 72 (1968) 1021-1027, doi: 10.1021 / j100849a041 .
23. ^ Bublitz, G .; Boxer, S .: Effective Polarity of Frozen Solvent Glasses in the Vicinity of Dipolar Solutes in J. Am. Chem. Soc. 120 (1998) 3988-3992, doi: 10.1021 / ja971665c .