Heptane, 2,2-dimethyl-
- Formula: C9H20
- Molecular weight: 128.2551
- IUPAC Standard InChIKey: PSABUFWDVWCFDP-UHFFFAOYSA-N
- CAS Registry Number: 1071-26-7
- 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. - Other names: 2,2-Dimethylheptane
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Henry's Law data
Go To: Top, Mass spectrum (electron ionization), Gas Chromatography, References, Notes
Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.
Data compiled by: Rolf Sander
Henry's Law constant (water solution)
kH(T) = k°H exp(d(ln(kH))/d(1/T) ((1/T) - 1/(298.15 K)))
k°H = Henry's law constant for solubility in water at 298.15 K (mol/(kg*bar))
d(ln(kH))/d(1/T) = Temperature dependence constant (K)
k°H (mol/(kg*bar)) | d(ln(kH))/d(1/T) (K) | Method | Reference | Comment |
---|---|---|---|---|
0.00021 | Q | N/A | missing citation give several references for the Henry's law constants but don't assign them to specific species. |
Mass spectrum (electron ionization)
Go To: Top, Henry's Law data, Gas Chromatography, References, Notes
Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.
Data compiled by: NIST Mass Spectrometry Data Center, William E. Wallace, director
Spectrum
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Additional Data
View image of digitized spectrum (can be printed in landscape orientation).
Due to licensing restrictions, this spectrum cannot be downloaded.
Owner | NIST Mass Spectrometry Data Center Collection (C) 2014 copyright by the U.S. Secretary of Commerce on behalf of the United States of America. All rights reserved. |
---|---|
NIST MS number | 2647 |
Gas Chromatography
Go To: Top, Henry's Law data, Mass spectrum (electron ionization), References, Notes
Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.
Data compiled by: NIST Mass Spectrometry Data Center, William E. Wallace, director
Kovats' RI, non-polar column, isothermal
Column type | Active phase | Temperature (C) | I | Reference | Comment |
---|---|---|---|---|---|
Capillary | Squalane | 100. | 816. | Heinzen, Soares, et al., 1999 | |
Capillary | Squalane | 25. | 815. | Hilal, Carreira, et al., 1994 | |
Capillary | OV-101 | 40. | 813. | Laub and Purnell, 1988 | |
Capillary | OV-101 | 60. | 815. | Laub and Purnell, 1988 | |
Capillary | OV-101 | 80. | 818. | Laub and Purnell, 1988 | |
Capillary | Squalane | 50. | 815.1 | Lunskii and Paizanskaya, 1988 | He; Column length: 50. m; Column diameter: 0.22 mm |
Capillary | Squalane | 70. | 816.1 | Lunskii and Paizanskaya, 1988 | He; Column length: 50. m; Column diameter: 0.22 mm |
Capillary | DB-1 | 60. | 820. | Lubeck and Sutton, 1983 | Column length: 60. m; Column diameter: 0.264 mm |
Capillary | DB-1 | 60. | 820. | Lubeck and Sutton, 1983 | 60. m/0.259 mm/1. μm |
Capillary | Squalane | 70. | 817.1 | Nabivach and Kirilenko, 1979 | N2; Column length: 50. m |
Capillary | Squalane | 60. | 816. | Chretien and Dubois, 1976 | |
Capillary | Squalane | 60. | 816.5 | Chretien and Dubois, 1976 | |
Capillary | Squalane | 100. | 817.1 | Lulova, Leont'eva, et al., 1976 | He; Column length: 120. m; Column diameter: 0.25 mm |
Capillary | Squalane | 100. | 817.7 | Lulova, Leont'eva, et al., 1976 | He; Column length: 120. m; Column diameter: 0.25 mm |
Packed | Apolane | 70. | 811.6 | Riedo, Fritz, et al., 1976 | He, Chromosorb; Column length: 2.4 m |
Capillary | Vacuum Grease Oil (VM-4) | 95. | 814.2 | Sultanov and Arustamova, 1975 | N2; Column length: 150. m; Column diameter: 0.25 mm |
Capillary | Squalane | 50. | 815. | Rijks and Cramers, 1974 | N2; Column length: 100. m; Column diameter: 0.25 mm |
Capillary | Squalane | 70. | 816. | Rijks and Cramers, 1974 | N2; Column length: 100. m; Column diameter: 0.25 mm |
Capillary | Vacuum Grease Oil (VM-4) | 35. | 810. | Sidorov, Petrova, et al., 1972 | |
Capillary | Vacuum Grease Oil (VM-4) | 45. | 811. | Sidorov, Petrova, et al., 1972 | |
Capillary | Vacuum Grease Oil (VM-4) | 50. | 811. | Sidorov, Petrova, et al., 1972 | |
Capillary | Vacuum Grease Oil (VM-4) | 58. | 812. | Sidorov, Petrova, et al., 1972 | |
Capillary | Vacuum Grease Oil (VM-4) | 68. | 813. | Sidorov, Petrova, et al., 1972 | |
Packed | SE-30 | 80. | 820. | Mitra and Saha, 1970 | N2 |
Packed | Squalane | 25. | 808. | Mitra and Saha, 1970 | N2 |
Capillary | Squalane | 60. | 816. | Matukuma, 1969 | N2; Column length: 91.4 m; Column diameter: 0.25 mm |
Capillary | Squalane | 80. | 817. | Schomburg, 1967 | Ar; Column length: 100. m |
Capillary | Squalane | 30. | 815. | Tourres, 1967 | H2; Column length: 100. m; Column diameter: 0.25 mm |
Capillary | Squalane | 50. | 816. | Tourres, 1967 | H2; Column length: 100. m; Column diameter: 0.25 mm |
Capillary | Squalane | 70. | 817. | Tourres, 1967 | H2; Column length: 100. m; Column diameter: 0.25 mm |
Kovats' RI, non-polar column, temperature ramp
Column type | Active phase | I | Reference | Comment |
---|---|---|---|---|
Capillary | OV-101 | 817. | Hayes and Pitzer, 1982 | 110. m/0.25 mm/0.20 μm, He, 1. K/min; Tstart: 35. C; Tend: 200. C |
Capillary | Apiezon L | 812. | Louis, 1971 | N2, 1. K/min; Column length: 50. m; Column diameter: 0.25 mm; Tstart: 60. C |
Kovats' RI, non-polar column, custom temperature program
Column type | Active phase | I | Reference | Comment |
---|---|---|---|---|
Capillary | Petrocol DH-100 | 829.9 | Haagen-Smit Laboratory, 1997 | He; Column length: 100. m; Column diameter: 0.2 mm; Program: 5C(10min) => 5C/min => 50C(48min) => 1.5C/min => 195C(91min) |
Capillary | Squalane | 816. | Korol and Lysyuk, 1980 | Program: not specified |
Van Den Dool and Kratz RI, non-polar column, temperature ramp
Column type | Active phase | I | Reference | Comment |
---|---|---|---|---|
Capillary | Petrocol DH | 824.7 | Censullo, Jones, et al., 2003 | 50. m/0.25 mm/0.5 μm, He, 35. C @ 10. min, 3. K/min, 200. C @ 10. min |
Capillary | OV-101 | 818.9 | Yin, Liu, et al., 2001 | N2, 1. K/min; Column length: 80. m; Column diameter: 0.22 mm; Tstart: 30. C; Tend: 130. C |
Capillary | Petrocol DH | 816.53 | Subramaniam, Bochniak, et al., 1994 | 100. m/0.25 mm/0.5 μm, He, 1. K/min; Tstart: 30. C; Tend: 220. C |
Capillary | Petrocol DH | 818.34 | Subramaniam, Bochniak, et al., 1994 | 100. m/0.25 mm/0.5 μm, He, 1. K/min; Tstart: 30. C; Tend: 220. C |
Capillary | Ultra-1 | 820. | Olson, Sinkevitch, et al., 1992 | 4. K/min; Tstart: -40. C; Tend: 230. C |
Capillary | Petrocol DH | 819. | White, Hackett, et al., 1992 | 100. m/0.25 mm/0.5 μm, He, 1. K/min; Tstart: 30. C; Tend: 220. C |
Capillary | OV-101 | 817. | Hayes and Pitzer, 1981 | 108. m/0.25 mm/0.2 μm, 1. K/min; Tstart: 35. C; Tend: 200. C |
Van Den Dool and Kratz RI, non-polar column, custom temperature program
Column type | Active phase | I | Reference | Comment |
---|---|---|---|---|
Capillary | OV-101 | 819. | Wu and Lu, 1984 | Program: not specified |
Normal alkane RI, non-polar column, isothermal
Column type | Active phase | Temperature (C) | I | Reference | Comment |
---|---|---|---|---|---|
Capillary | Methyl Silicone | 50. | 815. | N/A | N2; Column length: 74.6 m; Column diameter: 0.28 mm |
Capillary | OV-101 | 50. | 819. | Wu and Lu, 1984, 2 | |
Capillary | OV-101 | 70. | 820. | Wu and Lu, 1984, 2 | |
Capillary | Apiezon L | 40. to 190. | 818. | Mann, Mühlstädt, et al., 1967 | Column length: 2. m |
Capillary | Squalane | 70. | 817. | Schomburg, 1966 |
Normal alkane RI, non-polar column, temperature ramp
Column type | Active phase | I | Reference | Comment |
---|---|---|---|---|
Capillary | Polydimethyl siloxane: CP-Sil 5 CB | 820. | Bramston-Cook, 2013 | 60. m/0.25 mm/1.0 μm, Helium, 45. C @ 1.45 min, 3.6 K/min, 210. C @ 2.72 min |
Capillary | Petrocol DH | 818. | Supelco, 2012 | 100. m/0.25 mm/0.50 μm, Helium, 20. C @ 15. min, 15. K/min, 220. C @ 30. min |
Capillary | OV-101 | 818. | Orav, Kailas, et al., 1999 | 50. m/0.20 mm/0.50 μm, Helium, 30. C @ 6. min, 1. K/min; Tend: 100. C |
Normal alkane RI, non-polar column, custom temperature program
Column type | Active phase | I | Reference | Comment |
---|---|---|---|---|
Capillary | Methyl Silicone | 815. | Feng and Mu, 2007 | Program: not specified |
Capillary | OV-101 | 816. | Du and Liang, 2003 | Program: not specified |
Capillary | Polydimethyl siloxane | 816. | Junkes, Castanho, et al., 2003 | Program: not specified |
Capillary | Polydimethyl siloxanes | 819. | Yin, Guo, et al., 2001 | Program: not specified |
Capillary | Squalane | 814. | Petrov, 1984 | Program: not specified |
Capillary | OV-1, SE-30, Methyl silicone, SP-2100, OV-101, DB-1, etc. | 817. | Waggott and Davies, 1984 | Hydrogen; Column length: 50. m; Column diameter: 0.32 mm; Program: not specified |
References
Go To: Top, Henry's Law data, Mass spectrum (electron ionization), Gas Chromatography, Notes
Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.
Heinzen, Soares, et al., 1999
Heinzen, V.E.F.; Soares, M.F.; Yunes, R.A.,
Semi-empirical topological method for the prediction of the chromatographic retention of cis- and trans-alkene isomers and alkanes,
J. Chromatogr. A, 1999, 849, 2, 495-506, https://doi.org/10.1016/S0021-9673(99)00530-0
. [all data]
Hilal, Carreira, et al., 1994
Hilal, S.H.; Carreira, L.A.; Karickhoff, S.W.; Melton, C.M.,
Estimation of Gas-Liquid Chromatographic Retention Times from Molecular Structure,
J. Chromatogr. A, 1994, 662, 2, 269-280, https://doi.org/10.1016/0021-9673(94)80515-6
. [all data]
Laub and Purnell, 1988
Laub, R.J.; Purnell, J.H.,
Specific retention volumes, retention indices, and family-plot regressions of aliphatic, alicyclic, and aromatic hydrocarbon solutes with OV-101 poly (dimethylsiloxane) stationary phase,
J. Hi. Res. Chromatogr. Chromatogr. Comm., 1988, 11, 9, 649-660, https://doi.org/10.1002/jhrc.1240110908
. [all data]
Lunskii and Paizanskaya, 1988
Lunskii, M.Kh.; Paizanskaya, I.L.,
Identification of hydrocarbons C1-C9 of petrol fractions of oils and condensates in the use of capillary columns with dinonylphthalate,
Zh. Anal. Khim., 1988, 43, 127-135. [all data]
Lubeck and Sutton, 1983
Lubeck, A.J.; Sutton, DL.,
Kovats retention indices of selected hydrocarbons through C10 on bonded phase fused silica capillaries,
J. Hi. Res. Chromatogr. Chromatogr. Comm., 1983, 6, 6, 328-332, https://doi.org/10.1002/jhrc.1240060612
. [all data]
Nabivach and Kirilenko, 1979
Nabivach, V.M.; Kirilenko, A.V.,
The use of retention indices for identifying the components of crude benzene,
Solid Fuel Chem. (Engl. Transl.), 1979, 13, 3, 82-87. [all data]
Chretien and Dubois, 1976
Chretien, J.R.; Dubois, J.-E.,
New Perspectives in the Prediction of Kovats Indices,
J. Chromatogr., 1976, 126, 171-189, https://doi.org/10.1016/S0021-9673(01)84071-1
. [all data]
Lulova, Leont'eva, et al., 1976
Lulova, N.I.; Leont'eva, S.A.; Timofeeva, A.N.,
Gas-chromatographic method of determination of individual hydrocarbons in catalytic cracking gasolines
in Proceedings of All-Union Research Institute on Oil Processes. Vol.18, All-Union Research Institute on Oil Processes, Moscow, 1976, 30-53. [all data]
Riedo, Fritz, et al., 1976
Riedo, F.; Fritz, D.; Tarján, G.; Kováts, E.Sz.,
A tailor-made C87 hydrocarbon as a possible non-polar standard stationary phase for gas chromatography,
J. Chromatogr., 1976, 126, 63-83, https://doi.org/10.1016/S0021-9673(01)84063-2
. [all data]
Sultanov and Arustamova, 1975
Sultanov, N.T.; Arustamova, L.G.,
Determination of the boiling points of C10 isoalkanes in an n-decane isomerizate from gas chromatographic retention indices,
J. Chromatogr., 1975, 115, 2, 553-558, https://doi.org/10.1016/S0021-9673(01)98959-9
. [all data]
Rijks and Cramers, 1974
Rijks, J.A.; Cramers, C.A.,
High precision capillary gas chromatography of hydrocarbons,
Chromatographia, 1974, 7, 3, 99-106, https://doi.org/10.1007/BF02269819
. [all data]
Sidorov, Petrova, et al., 1972
Sidorov, R.I.; Petrova, V.I.; Ivanova, M.P.,
Qualitative analysis of wide-boiling fraction C5-C10 with capillary chromatography
in Processes in chromatographic columns. Vol.17, 1972, 14-25. [all data]
Mitra and Saha, 1970
Mitra, G.D.; Saha, N.C.,
Determination of Retention Indices of Saturated Hydrocarbons by Graphical Methods,
J. Chromatogr. Sci., 1970, 8, 2, 95-102, https://doi.org/10.1093/chromsci/8.2.95
. [all data]
Matukuma, 1969
Matukuma, A.,
Retention indices of alkanes through C10 and alkenes through C8 and relation between boiling points and retention data,
Gas Chromatogr., Int. Symp. Anal. Instrum. Div Instrum Soc. Amer., 1969, 7, 55-75. [all data]
Schomburg, 1967
Schomburg, G.,
Struktur und Retentionsverhalten von Offenkettigen und Cyclischen Kohlenwasserstoffen und Deren Einfacher Substitutionsprodukte,
Anal. Chim. Acta., 1967, 38, 45-64, https://doi.org/10.1016/S0003-2670(01)80560-2
. [all data]
Tourres, 1967
Tourres, D.A.,
Structure moléculaire et rétention en chromatographie en phase gazeuse. Influence de la température sur l'indice de rétention d'alcanes isomères,
J. Chromatogr., 1967, 30, 357-377, https://doi.org/10.1016/S0021-9673(00)84168-0
. [all data]
Hayes and Pitzer, 1982
Hayes, P.C., Jr.; Pitzer, E.W.,
Characterizing petroleum- and shale-derived jet fuel distillates via temperature-programmed Kováts indices,
J. Chromatogr., 1982, 253, 179-198, https://doi.org/10.1016/S0021-9673(01)88376-X
. [all data]
Louis, 1971
Louis, R.,
Kovats-index-tafeln zur gaschromatographischen analyse von kohlenwasserstoffgemischen,
Erdoel Kohle Erdgas Petrochem., 1971, 24, 2, 88-94. [all data]
Haagen-Smit Laboratory, 1997
Haagen-Smit Laboratory,
Procedure for the detailed hydrocarbon analysis of gasolines by single column high efficiency (capillary) column gas chromatography, SOP NO. MLD 118, Revision No. 1.1, California Environmental Protection Agency, Air Resources Board, El Monte, California, 1997, 22. [all data]
Korol and Lysyuk, 1980
Korol, A.N.; Lysyuk, L.S.,
A New Thermodynamic Method for Calculating the Retention Indices of Isoalkanes on Squalane,
Theor. Exp. Chem. (Engl. Transl.), 1980, 6, 577-584. [all data]
Censullo, Jones, et al., 2003
Censullo, A.C.; Jones, D.R.; Wills, M.T.,
Speciation of the volatile organic compounds (VOCs) in solventborne aerosol coatings by solid phase microextraction-gas chromatography,
J. Coat. Technol., 2003, 75, 936, 47-53, https://doi.org/10.1007/BF02697922
. [all data]
Yin, Liu, et al., 2001
Yin, C.; Liu, W.; Li, Z.; Pan, Z.; Lin, T.; Zhang, M.,
Chemometrics to chemical modeling: structural coding in hydrocarbons and retention indices of gas chromatography,
J. Sep. Sci., 2001, 24, 3, 213-220, https://doi.org/10.1002/1615-9314(20010301)24:3<213::AID-JSSC213>3.0.CO;2-4
. [all data]
Subramaniam, Bochniak, et al., 1994
Subramaniam, B.; Bochniak, D.; Snavely, K.,
Fischer-Tropsch synthesis in supercritical reaction media, Lawrence Department of Chemical and Petroleum Engineering (DOE/PC/92532--T7), United States Department of Energy, Pittsburgh, PA, 1994, 8, retrieved from http://www.NTIS.gov. [all data]
Olson, Sinkevitch, et al., 1992
Olson, K.L.; Sinkevitch, R.M.; Sloane, T.M.,
Speciation and Quantitation of Hydrocarbons in Gasoline Engine Exhaust,
J. Chromatogr. Sci., 1992, 30, 12, 500-508, https://doi.org/10.1093/chromsci/30.12.500
. [all data]
White, Hackett, et al., 1992
White, C.M.; Hackett, J.; Anderson, R.R.; Kail, S.; Spock, P.S.,
Linear temperature programmed retention indices of gasoline range hydrocarbons and chlorinated hydrocarbons on cross-linked polydimethylsiloxane,
J. Hi. Res. Chromatogr., 1992, 15, 2, 105-120, https://doi.org/10.1002/jhrc.1240150211
. [all data]
Hayes and Pitzer, 1981
Hayes, P.C., Jr.; Pitzer, E.W.,
Kovats indices as a tool in characterizing hydrocarbon fuels in temperature programmed glass capillary gas chromatography. Part 1. Qualitative identification, Inhouse rpt. for Air Force Wright Aeronautical Labs., Air Force Wright Aeronautical Labs., Wright-Patterson AFB, Ohio, 1981, 75. [all data]
Wu and Lu, 1984
Wu, J.; Lu, W.,
Hydrocarbon analysis by open-tubular column chromatography with programmed temperature for straight run gasoline,
Anal. Chem., 1984, 12, 7, 572-578. [all data]
Wu and Lu, 1984, 2
Wu, J.; Lu, W.,
Kovats indices of C4-C10 hydrocarbons in apolar quartz capillary OV-101,
Chin. J. Chromatogr., 1984, 1, 1, 11-17. [all data]
Mann, Mühlstädt, et al., 1967
Mann, G.; Mühlstädt, M.; Braband, J.; Döring, E.,
Konformation und physikalische daten von alkanen und cyclanen. II. Einfach und zweifach verzweigte alkane,
Tetrahedron, 1967, 23, 8, 3393-3401, https://doi.org/10.1016/S0040-4020(01)92305-1
. [all data]
Schomburg, 1966
Schomburg, G.,
Gaschromatographische Retentionsdaten und Struktur Chemischer Verbindungen. II. Methylverzweigungen und Doppelbindungen in Offenkettigen Kohlenwasserstoffen,
J. Chromatogr., 1966, 23, 1-17, https://doi.org/10.1016/S0021-9673(01)98652-2
. [all data]
Bramston-Cook, 2013
Bramston-Cook, R.,
Kovats indices for C2-C13 hydrocarbons and selected oxygenated/halocarbons with 100 % dimethylpolysiloxane columns, 2013, retrieved from http://lotusinstruments.com/monographs/List .... [all data]
Supelco, 2012
Supelco, CatalogNo. 24160-U,
Petrocol DH Columns. Catalog No. 24160-U, 2012, retrieved from http://www.sigmaaldrich.com/etc/medialib/docs/Supelco/Datasheet/1/w97949.Par.0001.File.tmp/w97949.pdf. [all data]
Orav, Kailas, et al., 1999
Orav, A.; Kailas, T.; Muurisepp, M.; Kann, J.,
Composition of the oil from waste tires. 1. Fraction boiling at yp to 160 0C,
Proc. Estonian Acad. Sci. Chem., 1999, 48, 1, 30-39. [all data]
Feng and Mu, 2007
Feng, H.; Mu, L.-L.,
Quantitative structure-retention relationships for alkane and its derivatives based on electrotopological state index and molecular shape index,
Chem. Ind. Engineering (Chinese), 2007, 24, 2, 161-168. [all data]
Du and Liang, 2003
Du, Y.; Liang, Y.,
Data mining for seeking accurate quantitative relationship between molecular structure and GC retention indices of alkanes by projection pursuit,
Comput. Biol. Chem., 2003, 27, 3, 339-353, https://doi.org/10.1016/S1476-9271(02)00081-6
. [all data]
Junkes, Castanho, et al., 2003
Junkes, B.S.; Castanho, R.D.M.; Amboni, C.; Yunes, R.A.; Heinzen, V.E.F.,
Semiempirical Topological Index: A Novel Molecular Descriptor for Quantitative Structure-Retention Relationship Studies,
Internet Electronic Journal of Molecular Design, 2003, 2, 1, 33-49. [all data]
Yin, Guo, et al., 2001
Yin, C.; Guo, W.; Lin, T.; Liu, S.; Fu, R.; Pan, Z.; Wang, L.,
Application of wavelet neural network to the prediction of gas chromatographic retention indices of alkanes,
J. Chinese Chem. Soc., 2001, 48, 739-749. [all data]
Petrov, 1984
Petrov, A.A.,
Hydrocarbons of petroleum, Nauka (publishing house), Moscow, 1984, 263. [all data]
Waggott and Davies, 1984
Waggott, A.; Davies, I.W.,
Identification of organic pollutants using linear temperature programmed retention indices (LTPRIs) - Part II, 1984, retrieved from http://dwi.defra.gov.uk/research/completed-research/reports/dwi0383.pdf. [all data]
Notes
Go To: Top, Henry's Law data, Mass spectrum (electron ionization), Gas Chromatography, References
- Symbols used in this document:
d(ln(kH))/d(1/T) Temperature dependence parameter for Henry's Law constant k°H Henry's Law constant at 298.15K - Data from NIST Standard Reference Database 69: NIST Chemistry WebBook
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