Dimethyl ether
- Formula: C2H6O
- Molecular weight: 46.0684
- IUPAC Standard InChIKey: LCGLNKUTAGEVQW-UHFFFAOYSA-N
- CAS Registry Number: 115-10-6
- Chemical structure:
This structure is also available as a 2d Mol file or as a computed 3d SD file
The 3d structure may be viewed using Java or Javascript. - Isotopologues:
- Other names: Methane, oxybis-; Methyl ether; Methoxymethane; Wood ether; Oxybismethane; (CH3)2O; Ether, dimethyl; Ether, methyl; UN 1033; Dimethyl oxide; Dymel A; Dymel; Demeon D; DME; Methane, 1,1'-oxybis-
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Phase change data
Go To: Top, Gas phase ion energetics data, References, Notes
Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.
Data compiled as indicated in comments:
BS - Robert L. Brown and Stephen E. Stein
TRC - Thermodynamics Research Center, NIST Boulder Laboratories, Chris Muzny director
AC - William E. Acree, Jr., James S. Chickos
DH - Eugene S. Domalski and Elizabeth D. Hearing
Quantity | Value | Units | Method | Reference | Comment |
---|---|---|---|---|---|
Tboil | 248.2 | K | N/A | Weast and Grasselli, 1989 | BS |
Tboil | 248.3 | K | N/A | Majer and Svoboda, 1985 | |
Tboil | 248.25 | K | N/A | Grosse, 1937 | Uncertainty assigned by TRC = 1. K; TRC |
Tboil | 249.2 | K | N/A | Maass and Boomer, 1922 | Uncertainty assigned by TRC = 0.4 K; TRC |
Tboil | 249.5 | K | N/A | Thiele and Schulte, 1920 | Uncertainty assigned by TRC = 0.6 K; TRC |
Quantity | Value | Units | Method | Reference | Comment |
Tfus | 135.2 | K | N/A | Maass and Boomer, 1922 | Uncertainty assigned by TRC = 2. K; TRC |
Quantity | Value | Units | Method | Reference | Comment |
Ttriple | 131.64 | K | N/A | Wilhoit, Chao, et al., 1985 | Uncertainty assigned by TRC = 0.05 K; TRC |
Ttriple | 131.66 | K | N/A | Kennedy, Sagenkahn, et al., 1941 | Uncertainty assigned by TRC = 0.06 K; TRC |
Quantity | Value | Units | Method | Reference | Comment |
Tc | 401. ± 2. | K | AVG | N/A | Average of 12 values; Individual data points |
Quantity | Value | Units | Method | Reference | Comment |
Pc | 54. ± 3. | bar | AVG | N/A | Average of 8 values; Individual data points |
Quantity | Value | Units | Method | Reference | Comment |
Vc | 0.164 | l/mol | N/A | Zawisza and Glowka, 1970 | Uncertainty assigned by TRC = 0.003 l/mol; TRC |
Quantity | Value | Units | Method | Reference | Comment |
ρc | 5.351 | mol/l | N/A | Edwards and Maass, 1935 | Uncertainty assigned by TRC = 0.43 mol/l; TRC |
ρc | 4.895 | mol/l | N/A | Tapp, Steacie, et al., 1933 | Uncertainty assigned by TRC = 0.65 mol/l; TRC |
ρc | 5.891 | mol/l | N/A | Cardoso and Coppola, 1923 | Uncertainty assigned by TRC = 0.07 mol/l; extraplation of rectilinear diameter, from obs L and G densities, to Tc = 126.9 deg C, from previous literature; TRC |
Quantity | Value | Units | Method | Reference | Comment |
ΔvapH° | 19.3 | kJ/mol | N/A | Majer and Svoboda, 1985 | |
ΔvapH° | 18.5 | kJ/mol | N/A | Ambrose, Ellender, et al., 1976 | Based on data from 171. to 248. K.; AC |
Enthalpy of vaporization
ΔvapH (kJ/mol) | Temperature (K) | Method | Reference | Comment |
---|---|---|---|---|
21.510 | 248.34 | N/A | Kennedy, Sagenkahn, et al., 1941, 2 | P = 101.325 kPa; DH |
21.51 | 248.3 | N/A | Majer and Svoboda, 1985 | |
22.6 | 250. | A | Stephenson and Malanowski, 1987 | Based on data from 183. to 265. K.; AC |
22.8 | 234. | A | Stephenson and Malanowski, 1987 | Based on data from 180. to 249. K.; AC |
21.2 | 308. | A | Stephenson and Malanowski, 1987 | Based on data from 293. to 360. K.; AC |
21.1 | 364. | A | Stephenson and Malanowski, 1987 | Based on data from 349. to 400. K.; AC |
22.2 | 256. | A | Stephenson and Malanowski, 1987 | Based on data from 241. to 303. K.; AC |
21.4 | 248. | N/A | Ambrose, Ellender, et al., 1976 | Based on data from 171. to 248. K.; AC |
22.7 | 233. | N/A | Kennedy, Sagenkahn, et al., 1941, 2 | Based on data from 195. to 248. K.; AC |
21.5 ± 0.1 | 248. | C | Kennedy, Sagenkahn, et al., 1941, 2 | AC |
Entropy of vaporization
ΔvapS (J/mol*K) | Temperature (K) | Reference | Comment |
---|---|---|---|
86.61 | 248.34 | Kennedy, Sagenkahn, et al., 1941, 2 | P; DH |
Antoine Equation Parameters
log10(P) = A − (B / (T + C))
P = vapor pressure (bar)
T = temperature (K)
View plot Requires a JavaScript / HTML 5 canvas capable browser.
Temperature (K) | A | B | C | Reference | Comment |
---|---|---|---|---|---|
194.93 to 248.24 | 4.11475 | 894.669 | -30.604 | Kennedy, Sagenkahn, et al., 1941, 2 | Coefficents calculated by NIST from author's data. |
Enthalpy of fusion
ΔfusH (kJ/mol) | Temperature (K) | Reference | Comment |
---|---|---|---|
4.9363 | 131.66 | Kennedy, Sagenkahn, et al., 1941, 2 | DH |
4.94 | 131.7 | Domalski and Hearing, 1996 | AC |
Entropy of fusion
ΔfusS (J/mol*K) | Temperature (K) | Reference | Comment |
---|---|---|---|
37.49 | 131.66 | Kennedy, Sagenkahn, et al., 1941, 2 | DH |
Gas phase ion energetics data
Go To: Top, Phase change data, References, Notes
Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.
Data evaluated as indicated in comments:
HL - Edward P. Hunter and Sharon G. Lias
L - Sharon G. Lias
Data compiled as indicated in comments:
B - John E. Bartmess
LBLHLM - Sharon G. Lias, John E. Bartmess, Joel F. Liebman, John L. Holmes, Rhoda D. Levin, and W. Gary Mallard
LLK - Sharon G. Lias, Rhoda D. Levin, and Sherif A. Kafafi
RDSH - Henry M. Rosenstock, Keith Draxl, Bruce W. Steiner, and John T. Herron
View reactions leading to C2H6O+ (ion structure unspecified)
Quantity | Value | Units | Method | Reference | Comment |
---|---|---|---|---|---|
IE (evaluated) | 10.025 ± 0.025 | eV | N/A | N/A | L |
Quantity | Value | Units | Method | Reference | Comment |
Proton affinity (review) | 792. | kJ/mol | N/A | Hunter and Lias, 1998 | HL |
Quantity | Value | Units | Method | Reference | Comment |
Gas basicity | 764.5 | kJ/mol | N/A | Hunter and Lias, 1998 | HL |
Ionization energy determinations
IE (eV) | Method | Reference | Comment |
---|---|---|---|
10.025 ± 0.025 | PIPECO | Butler, Holland, et al., 1984 | LBLHLM |
9.95 ± 0.07 | EI | Bowen and Maccoll, 1984 | LBLHLM |
10.04 | PE | Kimura, Katsumata, et al., 1981 | LLK |
9.8 ± 0.1 | PE | Aue, Webb, et al., 1980 | LLK |
9.8 | PE | Aue and Bowers, 1979 | LLK |
10.01 ± 0.01 | PI | Botter, Pechine, et al., 1977 | LLK |
9.94 ± 0.01 | PE | Cocksey, Eland, et al., 1971 | LLK |
10.1 ± 0.2 | EI | Ivko, 1970 | RDSH |
9.94 | PE | Dewar and Worley, 1969 | RDSH |
9.96 ± 0.05 | S | Hernandez, 1963 | RDSH |
10.00 ± 0.02 | PI | Watanabe, 1957 | RDSH |
10.0 | PE | Bajic, Humski, et al., 1985 | Vertical value; LBLHLM |
10.1 | PE | Bieri, Asbrink, et al., 1982 | Vertical value; LBLHLM |
11.94 | PE | Utsunomiya, Kobayashi, et al., 1980 | Vertical value; LLK |
10.0 ± 0.2 | PE | Carnovale, Livett, et al., 1980 | Vertical value; LLK |
10.1 | PE | Aue and Bowers, 1979 | Vertical value; LLK |
10.03 | PE | Kobayashi, 1978 | Vertical value; LLK |
9.98 | PE | Benoit and Harrison, 1977 | Vertical value; LLK |
10.052 | PE | Aue, Webb, et al., 1975 | Vertical value; LLK |
10.04 | PE | Bock, Mollere, et al., 1973 | Vertical value; LLK |
10.04 | PE | Cradock and Whiteford, 1972 | Vertical value; LLK |
Appearance energy determinations
Ion | AE (eV) | Other Products | Method | Reference | Comment |
---|---|---|---|---|---|
CHO+ | ≤12.85 ± 0.10 | H2+CH3 | PIPECO | Butler, Holland, et al., 1984 | T = 298K; LBLHLM |
CHO+ | 14.0 ± 0.2 | ? | EI | Ivko, 1970 | RDSH |
CH3+ | ≤14.4 ± 0.1 | CH2O+H | PIPECO | Butler, Holland, et al., 1984 | T = 298K; LBLHLM |
CH3+ | 14.93 ± 0.13 | ? | EI | Haney and Franklin, 1969 | RDSH |
CH3O+ | ≤11.85 ± 0.10 | CH3 | PIPECO | Butler, Holland, et al., 1984 | T = 298K; LBLHLM |
CH3O+ | ≤11.8 | CH3 | EI | Lossing, 1977 | LLK |
CH3O+ | 12.4 ± 0.1 | CH3 | EI | Ivko, 1970 | RDSH |
CH3O+ | 11.95 ± 0.05 | CH3 | EI | Haney and Franklin, 1969 | RDSH |
C2H5O+ | 11.115 ± 0.010 | H | PIPECO | Butler, Holland, et al., 1984 | T = 0K; LBLHLM |
C2H5O+ | 10.99 ± 0.08 | H | EI | Bowen and Maccoll, 1984 | LBLHLM |
C2H5O+ | 10.99 | H | EI | Lossing, 1977 | LLK |
C2H5O+ | 11.23 ± 0.04 | H | EI | Solka and Russell, 1974 | LLK |
C2H5O+ | 10.70 ± 0.13 | H | EI | Finney and Harrison, 1972 | LLK |
C2H5O+ | 11.55 ± 0.15 | H | EI | Ivko, 1970 | RDSH |
C2H5O+ | 11.42 ± 0.01 | H | EI | Martin, Lampe, et al., 1966 | RDSH |
De-protonation reactions
C2H5O- + =
By formula: C2H5O- + H+ = C2H6O
Quantity | Value | Units | Method | Reference | Comment |
---|---|---|---|---|---|
ΔrH° | 1703. ± 8.4 | kJ/mol | Bran | DePuy, Bierbaum, et al., 1984 | gas phase; B |
Quantity | Value | Units | Method | Reference | Comment |
ΔrG° | 1666. ± 9.2 | kJ/mol | H-TS | DePuy, Bierbaum, et al., 1984 | gas phase; B |
References
Go To: Top, Phase change data, Gas phase ion energetics data, Notes
Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.
Weast and Grasselli, 1989
CRC Handbook of Data on Organic Compounds, 2nd Editon, Weast,R.C and Grasselli, J.G., ed(s)., CRC Press, Inc., Boca Raton, FL, 1989, 1. [all data]
Majer and Svoboda, 1985
Majer, V.; Svoboda, V.,
Enthalpies of Vaporization of Organic Compounds: A Critical Review and Data Compilation, Blackwell Scientific Publications, Oxford, 1985, 300. [all data]
Grosse, 1937
Grosse, A.V.,
Refractive Indices at Low Temperatures,
J. Am. Chem. Soc., 1937, 59, 2739-41. [all data]
Maass and Boomer, 1922
Maass, O.; Boomer, E.H.,
Vapor Densities at Low Pressures and Over and Extended Temperature Range. I. The Properties of Ethylene Oxide Compared to Oxygen Compounds of Similar Molecular Weight,
J. Am. Chem. Soc., 1922, 44, 8, 1709-1728, https://doi.org/10.1021/ja01429a013
. [all data]
Thiele and Schulte, 1920
Thiele, A.; Schulte, E.,
Binary equilibrium systems with solid carbon dioxide,
Z. Phys. Chem., Stoechiom. Verwandtschaftsl., 1920, 96, 312-42. [all data]
Wilhoit, Chao, et al., 1985
Wilhoit, R.C.; Chao, J.; Hall, K.R.,
Thermodynamic Properties of Key Organic Compounds in the Carbon Range C1 to C4. Part 1. Properties of Condensed Phases,
J. Phys. Chem. Ref. Data, 1985, 14, 1. [all data]
Kennedy, Sagenkahn, et al., 1941
Kennedy, R.M.; Sagenkahn, M.; Aston, J.G.,
The Heat Capacity and Entropy, Heats of Fusion and Vaporization and the Vapor Pressure of Dimethyl Ether. The Density of Gaseous Dimethyl Ether,
J. Am. Chem. Soc., 1941, 63, 2267-72. [all data]
Zawisza and Glowka, 1970
Zawisza, A.C.; Glowka, S.,
Liquid-vapour equilibria and thermodynamic functions of dimethyl ether - sulphur dioxide system up to 300c and 77.81 atmospheres,
Bull. Acad. Pol. Sci., Ser. Sci. Chim., 1970, 18, 549-54. [all data]
Edwards and Maass, 1935
Edwards, J.; Maass, O.,
Density and Adsorption Studies in the Region of the Critical Temperature: System Dimethyl-ether-alumina.,
Can. J. Res., Sect. A, 1935, 12, 357-71. [all data]
Tapp, Steacie, et al., 1933
Tapp, J.S.; Steacie, E.W.R.; Maass, O.,
Density of a Vapor in Equilibrium with a Liquid Near the Critical Temperature.,
Can. J. Res., 1933, 9, 217-39. [all data]
Cardoso and Coppola, 1923
Cardoso, E.; Coppola, A.A.,
Experimental researches on some thermal properties of gas I the densities of coexisting phases of methyl ether,
J. Chim. Phys. Phys.-Chim. Biol., 1923, 20, 337-46. [all data]
Ambrose, Ellender, et al., 1976
Ambrose, D.; Ellender, J.H.; Sprake, C.H.S.; Townsend, R.,
Thermodynamic properties of organic oxygen compounds XLIII. Vapour pressures of some ethers,
The Journal of Chemical Thermodynamics, 1976, 8, 2, 165-178, https://doi.org/10.1016/0021-9614(76)90090-2
. [all data]
Kennedy, Sagenkahn, et al., 1941, 2
Kennedy, R.M.; Sagenkahn, M.; Aston, J.G.,
The heat capacity and entropy, heats of fusion and vaporization, and the vapor pressure of dimethyl ether. The density of gaseous dimethyl ether,
J. Am. Chem. Soc., 1941, 63, 2267-2272. [all data]
Stephenson and Malanowski, 1987
Stephenson, Richard M.; Malanowski, Stanislaw,
Handbook of the Thermodynamics of Organic Compounds, 1987, https://doi.org/10.1007/978-94-009-3173-2
. [all data]
Domalski and Hearing, 1996
Domalski, Eugene S.; Hearing, Elizabeth D.,
Heat Capacities and Entropies of Organic Compounds in the Condensed Phase. Volume III,
J. Phys. Chem. Ref. Data, 1996, 25, 1, 1, https://doi.org/10.1063/1.555985
. [all data]
Hunter and Lias, 1998
Hunter, E.P.; Lias, S.G.,
Evaluated Gas Phase Basicities and Proton Affinities of Molecules: An Update,
J. Phys. Chem. Ref. Data, 1998, 27, 3, 413-656, https://doi.org/10.1063/1.556018
. [all data]
Butler, Holland, et al., 1984
Butler, J.J.; Holland, D.M.P.; Parr, A.C.; Stockbauer, R.,
A threshold photoelectron-photoion coincidence spectrometric study of dimethyl ether (CH3OCH3),
Int. J. Mass Spectrom. Ion Processes, 1984, 58, 1. [all data]
Bowen and Maccoll, 1984
Bowen, R.D.; Maccoll, A.,
Low energy, low temperature mass spectra,
Org. Mass Spectrom., 1984, 19, 379. [all data]
Kimura, Katsumata, et al., 1981
Kimura, K.; Katsumata, S.; Achiba, Y.; Yamazaki, T.; Iwata, S.,
Ionization energies, Ab initio assignments, and valence electronic structure for 200 molecules
in Handbook of HeI Photoelectron Spectra of Fundamental Organic Compounds, Japan Scientific Soc. Press, Tokyo, 1981. [all data]
Aue, Webb, et al., 1980
Aue, D.H.; Webb, H.M.; Davidson, W.R.; Vidal, M.; Bowers, M.T.; Goldwhite, H.; Vertal, L.E.; Douglas, J.E.; Kollman, P.A.; Kenyon, G.L.,
Proton affinities photoelectron spectra of three-membered-ring J. Heterocycl. Chem.,
J. Am. Chem. Soc., 1980, 102, 5151. [all data]
Aue and Bowers, 1979
Aue, D.H.; Bowers, M.T.,
Chapter 9. Stabilities of positive ions from equilibrium gas phase basicity measurements
in Ions Chemistry,, ed. M.T. Bowers, 1979. [all data]
Botter, Pechine, et al., 1977
Botter, R.; Pechine, J.M.; Rosenstock, H.M.,
Photoionization of dimethyl ether and diethyl ether,
Int. J. Mass Spectrom. Ion Phys., 1977, 25, 7. [all data]
Cocksey, Eland, et al., 1971
Cocksey, B.J.; Eland, J.H.D.; Danby, C.J.,
The effect of alkyl substitution on ionisation potential,
J. Chem. Soc., 1971, (B), 790. [all data]
Ivko, 1970
Ivko, A.A.,
Use of mass spectroscopy and isotope labelling for determining the structure of ions and molecules,
Org. Katal., 1970, 20. [all data]
Dewar and Worley, 1969
Dewar, M.J.S.; Worley, S.D.,
Photoelectron spectra of molecules. I. Ionization potentials of some organic molecules and their interpretation,
J. Chem. Phys., 1969, 50, 654. [all data]
Hernandez, 1963
Hernandez, G.J.,
Vacuum ultraviolet absorption spectrum of dimethyl ether,
J. Chem. Phys., 1963, 38, 1644. [all data]
Watanabe, 1957
Watanabe, K.,
Ionization potentials of some molecules,
J. Chem. Phys., 1957, 26, 542. [all data]
Bajic, Humski, et al., 1985
Bajic, M.; Humski, K.; Klasinc, L.; Ruscic, B.,
Substitution effects on electronic structure of thiophene,
Z. Naturforsch. B:, 1985, 40, 1214. [all data]
Bieri, Asbrink, et al., 1982
Bieri, G.; Asbrink, L.; Von Niessen, W.,
30.4-nm He(II) photoelectron spectra of organic molecules,
J. Electron Spectrosc. Relat. Phenom., 1982, 27, 129. [all data]
Utsunomiya, Kobayashi, et al., 1980
Utsunomiya, C.; Kobayashi, T.; Nagakura, S.,
Photoelectron angular distribution measurements for some aliphatic alcohols, amines, halides,
Bull. Chem. Soc. Jpn., 1980, 53, 1216. [all data]
Carnovale, Livett, et al., 1980
Carnovale, F.; Livett, M.K.; Peel, J.B.,
The photoelectron spectrum of the dimethyl ether-hydrogen chloride complex,
J. Am. Chem. Soc., 1980, 102, 569. [all data]
Kobayashi, 1978
Kobayashi, T.,
A simple general tendency in photoelectron angular distributions of some monosubstituted benzenes,
Phys. Lett., 1978, 69, 105. [all data]
Benoit and Harrison, 1977
Benoit, F.M.; Harrison, A.G.,
Predictive value of proton affinity. Ionization energy correlations involving oxygenated molecules,
J. Am. Chem. Soc., 1977, 99, 3980. [all data]
Aue, Webb, et al., 1975
Aue, D.H.; Webb, H.M.; Bowers, M.T.,
Proton affinities, ionization potentials, and hydrogen affinities of nitrogen and oxygen bases. Hybridization effects,
J. Am. Chem. Soc., 1975, 97, 4137. [all data]
Bock, Mollere, et al., 1973
Bock, H.; Mollere, P.; Becker, G.; Fritz, G.,
Photoelectron spectra molecular properties. XX. Dimethyl ether, methoxysilane, and disiloxane,
J. Organomet. Chem., 1973, 61, 113. [all data]
Cradock and Whiteford, 1972
Cradock, S.; Whiteford, R.A.,
Photoelectron spectra of the methyl, silyl and germyl derivatives of the group VI elements,
J. Chem. Soc. Faraday Trans. 2, 1972, 68, 281. [all data]
Haney and Franklin, 1969
Haney, M.A.; Franklin, J.L.,
Excess energies in mass spectra of some oxygen-containing organic compounds,
J. Chem. Soc. Faraday Trans., 1969, 65, 1794. [all data]
Lossing, 1977
Lossing, F.P.,
Heats of formation of some isomeric [CnH2n+1]+ ions. Substitutional effects on ion stability,
J. Am. Chem. Soc., 1977, 99, 7526. [all data]
Solka and Russell, 1974
Solka, B.H.; Russell, M.E.,
Energetics of formation of some structural isomers of gaseous C2H5O+ C2H6N+ ions,
J. Phys. Chem., 1974, 78, 1268. [all data]
Finney and Harrison, 1972
Finney, C.D.; Harrison, A.G.,
A third-derivative method for determining electron-impact onset potentials,
Int. J. Mass Spectrom. Ion Phys., 1972, 9, 221. [all data]
Martin, Lampe, et al., 1966
Martin, R.H.; Lampe, F.W.; Taft, R.W.,
An electron-impact study of ionization and dissociation in methoxy- and halogen- substituted methanes,
J. Am. Chem. Soc., 1966, 88, 1353. [all data]
DePuy, Bierbaum, et al., 1984
DePuy, C.H.; Bierbaum, V.M.; Damrauer, R.,
Relative Gas-Phase Acidities of the Alkanes,
J. Am. Chem. Soc., 1984, 106, 4051. [all data]
Notes
Go To: Top, Phase change data, Gas phase ion energetics data, References
- Symbols used in this document:
AE Appearance energy IE (evaluated) Recommended ionization energy Pc Critical pressure Tboil Boiling point Tc Critical temperature Tfus Fusion (melting) point Ttriple Triple point temperature Vc Critical volume ΔfusH Enthalpy of fusion ΔfusS Entropy of fusion ΔrG° Free energy of reaction at standard conditions ΔrH° Enthalpy of reaction at standard conditions ΔvapH Enthalpy of vaporization ΔvapH° Enthalpy of vaporization at standard conditions ΔvapS Entropy of vaporization ρc Critical density - Data from NIST Standard Reference Database 69: NIST Chemistry WebBook
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