Trimethylaluminum

Formula: C₃H₉Al
Molecular weight: 72.0851
IUPAC Standard InChI: InChI=1S/3CH3.Al/h3*1H3;
IUPAC Standard InChIKey: JLTRXTDYQLMHGR-UHFFFAOYSA-N
CAS Registry Number: 75-24-1
Chemical structure:
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Other names: (CH3)3Al; Aluminum, trimethyl-; Trimethylalane; Trimethylaluminium; UN 1103
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Gas phase thermochemistry data

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Data compiled by: José A. Martinho Simões

Quantity	Value	Units	Method	Reference	Comment
Δ_fH°_gas	-86.5 ± 4.8	kJ/mol	Review	Martinho Simões	Selected data. The enthalpy of formation relies on -1891.3 ± 1.9 kJ/mol for the enthalpy of formation of Al(OOCMe)3(cr) and on 0.9 ± 0.2 kJ/mol for the enthalpy of solution of MeCOOH(l) in toluene Mortimer and Sellers, 1963. Liquid trimethylaluminum contains a very small molar fraction of monomer at 298 K, ca. 0.007% Smith, 1972, so that the "real" liquid should be described as [Al(Me)3]2.
Δ_fH°_gas	-57.0 ± 9.7	kJ/mol	Review	Martinho Simões	Liquid trimethylaluminum contains a very small molar fraction of monomer at 298 K, ca. 0.007% Smith, 1972, so that the "real" liquid should be described as [Al(Me)3]2.
Δ_fH°_gas	-88.7	kJ/mol	Review	Martinho Simões	The enthalpy of formation was quoted from Smith, 1974 and relies on experimental data in Tröber and Stricker, 1966. Liquid trimethylaluminum contains a very small molar fraction of monomer at 298 K, ca. 0.007% Smith, 1972, so that the "real" liquid should be described as [Al(Me)3]2.

Condensed phase thermochemistry data

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Data compiled as indicated in comments:
MS - José A. Martinho Simões
DH - Eugene S. Domalski and Elizabeth D. Hearing

Quantity	Value	Units	Method	Reference	Comment
Δ_fH°_liquid	-149.7 ± 4.5	kJ/mol	Review	Martinho Simões	Selected data. The enthalpy of formation relies on -1891.3 ± 1.9 kJ/mol for the enthalpy of formation of Al(OOCMe)3(cr) and on 0.9 ± 0.2 kJ/mol for the enthalpy of solution of MeCOOH(l) in toluene Mortimer and Sellers, 1963. Liquid trimethylaluminum contains a very small molar fraction of monomer at 298 K, ca. 0.007% Smith, 1972, so that the "real" liquid should be described as [Al(Me)3]2.; MS
Δ_fH°_liquid	-120.2 ± 9.6	kJ/mol	Review	Martinho Simões	Liquid trimethylaluminum contains a very small molar fraction of monomer at 298 K, ca. 0.007% Smith, 1972, so that the "real" liquid should be described as [Al(Me)3]2.; MS
Δ_fH°_liquid	-151.9	kJ/mol	CC-SB	Smith, 1974	Value corrected based on a set of ancillary data by J.A. Martinho Sim�es; The enthalpy of formation was quoted from Smith, 1974 and relies on experimental data in Tröber and Stricker, 1966. Liquid trimethylaluminum contains a very small molar fraction of monomer at 298 K, ca. 0.007% Smith, 1972, so that the "real" liquid should be described as [Al(Me)3]2.; MS
Quantity	Value	Units	Method	Reference	Comment
Δ_cH°_liquid	-3184.4 ± 9.6	kJ/mol	CC-SB	Long and Norrish, 1949	Please also see Cox and Pilcher, 1970. Liquid trimethylaluminum contains a very small molar fraction of monomer at 298 K, ca. 0.007% Smith, 1972, so that the "real" liquid should be described as [Al(Me)3]2.; MS
Quantity	Value	Units	Method	Reference	Comment
S°_liquid	209.41	J/mol*K	N/A	McCullough, Messerly, et al., 1963	DH

Constant pressure heat capacity of liquid

C_p,liquid (J/mol*K)	Temperature (K)	Reference	Comment
155.60	298.15	McCullough, Messerly, et al., 1963	T = 10 to 380 K.; DH

Gas phase ion energetics data

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Data compiled as indicated in comments:
LLK - Sharon G. Lias, Rhoda D. Levin, and Sherif A. Kafafi
RDSH - Henry M. Rosenstock, Keith Draxl, Bruce W. Steiner, and John T. Herron

Ionization energy determinations

IE (eV)	Method	Reference	Comment
9.09 ± 0.26	EI	Winters and Kiser, 1967	RDSH
9.76	PE	Barker, Lappert, et al., 1975	Vertical value; LLK

Appearance energy determinations

Ion	AE (eV)	Other Products	Method	Reference	Comment
Al⁺	14.6 ± 0.2	?	EI	Winters and Kiser, 1967	RDSH
CH₃Al⁺	13.9 ± 0.3	?	EI	Winters and Kiser, 1967	RDSH
C₂H₆Al⁺	10.1 ± 0.3	CH₃	EI	Winters and Kiser, 1967	RDSH

References

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Martinho Simões
Martinho Simões, J.A., Private communication (see http://webbook.nist.gov/chemistry/om/). [all data]

Mortimer and Sellers, 1963
Mortimer, C.T.; Sellers, P., J. Chem. Soc., 1963, 1978.. [all data]

Smith, 1972
Smith, M.B., J. Organometal. Chem., 1972, 46, 31. [all data]

Smith, 1974
Smith, M.B., J. Organometal. Chem., 1974, 76, 171. [all data]

Tröber and Stricker, 1966
Tröber, A.; Stricker, C., Wiss Z. Tech. Hochsch. Chem. "Carl Schlorlemmer" Leuna-Merseburg, 1966, 8, 34. [all data]

Long and Norrish, 1949
Long, L.H.; Norrish, R.G.W., Phil. Trans. Roy. Soc. (London), 1949, A241, 587. [all data]

Cox and Pilcher, 1970
Cox, J.D.; Pilcher, G., Thermochemistry of Organic and Organometallic Compounds in Academic Press, New York, 1970. [all data]

McCullough, Messerly, et al., 1963
McCullough, J.P.; Messerly, J.F.; Moore, R.T.; Todd, S.S., Trimethylaluminum: thermodynamic functions in the solid and liquid states, 0-380°K, vapor pressure, heat of vaporization, and entropy in the ideal gas state, J. Phys. Chem., 1963, 67, 677-679. [all data]

Winters and Kiser, 1967
Winters, R.E.; Kiser, R.W., Ionization and fragmentation of dimethylzinc, trimethylaluminum, and trimethylantimony, J. Organometal. Chem., 1967, 10, 7. [all data]

Barker, Lappert, et al., 1975
Barker, G.K.; Lappert, M.F.; Pedley, J.B.; Sharp, G.J.; Westwood, N.P.C., Bonding studies of boron and the group 3-5 elements. Part XV. He(I) photoelectron spectra of monomeric group 3 tri-halide, trimethyl, and mixed halogenomethyl species, J. Chem. Soc. Dalton Trans., 1975, 1765. [all data]

Notes

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Symbols used in this document:

AE	Appearance energy
C_p,liquid	Constant pressure heat capacity of liquid
S°_liquid	Entropy of liquid at standard conditions
Δ_cH°_liquid	Enthalpy of combustion of liquid at standard conditions
Δ_fH°_gas	Enthalpy of formation of gas at standard conditions
Δ_fH°_liquid	Enthalpy of formation of liquid at standard conditions

Data from NIST Standard Reference Database 69: NIST Chemistry WebBook
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