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:
This structure is also available as a 2d Mol file or as a computed 3d SD file
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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	-20.7 ± 1.1	kcal/mol	Review	Martinho Simões	Selected data. The enthalpy of formation relies on -452.03 ± 0.45 kcal/mol for the enthalpy of formation of Al(OOCMe)3(cr) and on 0.2 ± 0.05 kcal/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	-13.6 ± 2.3	kcal/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	-21.2	kcal/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	-35.8 ± 1.1	kcal/mol	Review	Martinho Simões	Selected data. The enthalpy of formation relies on -452.03 ± 0.45 kcal/mol for the enthalpy of formation of Al(OOCMe)3(cr) and on 0.2 ± 0.05 kcal/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	-28.7 ± 2.3	kcal/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	-36.30	kcal/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	-761.1 ± 2.3	kcal/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	50.050	cal/mol*K	N/A	McCullough, Messerly, et al., 1963	DH

Constant pressure heat capacity of liquid

C_p,liquid (cal/mol*K)	Temperature (K)	Reference	Comment
37.189	298.15	McCullough, Messerly, et al., 1963	T = 10 to 380 K.; DH

Phase change data

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Data compiled as indicated in comments:
TRC - Thermodynamics Research Center, NIST Boulder Laboratories, Chris Muzny director
MS - José A. Martinho Simões
AC - William E. Acree, Jr., James S. Chickos
DH - Eugene S. Domalski and Elizabeth D. Hearing

Quantity	Value	Units	Method	Reference	Comment
T_triple	288.43	K	N/A	McCullough, Messerly, et al., 1963, 2	Uncertainty assigned by TRC = 0.02 K; TRC
Quantity	Value	Units	Method	Reference	Comment
Δ_vapH°	15.1 ± 0.41	kcal/mol	RSC	McCullough, Messerly, et al., 1963, 2	MS

Enthalpy of vaporization

Δ_vapH (kcal/mol)	Temperature (K)	Reference	Comment
10.3	288. to 293.	Fulem, Ruzicka, et al., 2003	AC
9.51	351.	McCullough, Messerly, et al., 1963	Based on data from 336. to 400. K.; AC

Antoine Equation Parameters

log₁₀(P) = A − (B / (T + C))
P = vapor pressure (atm)
T = temperature (K)

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Temperature (K)	A	B	C	Reference	Comment
336.96 to 400.27	4.67413	1724.231	-31.398	McCullough, Messerly, et al., 1963	Coefficents calculated by NIST from author's data.

Enthalpy of sublimation

Δ_subH (kcal/mol)	Temperature (K)	Reference	Comment
14.4	243. to 285.	Fulem, Ruzicka, et al., 2003	AC

Enthalpy of fusion

Δ_fusH (kcal/mol)	Temperature (K)	Reference	Comment
2.1010	288.43	McCullough, Messerly, et al., 1963	DH
2.10	288.4	Domalski and Hearing, 1996	AC

Entropy of fusion

Δ_fusS (cal/mol*K)	Temperature (K)	Reference	Comment
7.285	288.43	McCullough, Messerly, et al., 1963	DH

In addition to the Thermodynamics Research Center (TRC) data available from this site, much more physical and chemical property data is available from the following TRC products:

Reaction thermochemistry data

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Data compiled as indicated in comments:
B - John E. Bartmess
MS - José A. Martinho Simões

Note: Please consider using the reaction search for this species. This page allows searching of all reactions involving this species. A general reaction search form is also available. Future versions of this site may rely on reaction search pages in place of the enumerated reaction displays seen below.

Individual Reactions

+ Trimethylaluminum = ( • )

By formula: H^- + C₃H₉Al = (H^- • C₃H₉Al)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	>84.80 ± 0.50	kcal/mol	IMRB	den Berg, Ingemann, et al., 1992	gas phase; Hydride affinity > (CF3)2CO. Computations indicate HOF(A-) ca. -46 kcal/mol, dHaff ca. 74 kcal/mol; B

C₆H₁₈Al₂ (l) = 2 Trimethylaluminum (l)

By formula: C₆H₁₈Al₂ (l) = 2C₃H₉Al (l)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	19.4 ± 0.31	kcal/mol	EqS	Smith, 1972	MS

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

Ion clustering data

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Data compiled by: John E. Bartmess

Note: Please consider using the reaction search for this species. This page allows searching of all reactions involving this species. Searches may be limited to ion clustering reactions. A general reaction search form is also available.

Clustering reactions

+ Trimethylaluminum = ( • )

By formula: H^- + C₃H₉Al = (H^- • C₃H₉Al)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	>84.80 ± 0.50	kcal/mol	IMRB	den Berg, Ingemann, et al., 1992	gas phase; Hydride affinity > (CF3)2CO. Computations indicate HOF(A-) ca. -46 kcal/mol, dHaff ca. 74 kcal/mol

Mass spectrum (electron ionization)

Go To: Top, Gas phase thermochemistry data, Condensed phase thermochemistry data, Phase change data, Reaction thermochemistry data, Gas phase ion energetics data, Ion clustering data, References, Notes

Data compiled by: NIST Mass Spectrometry Data Center, William E. Wallace, director

Spectrum

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Additional Data

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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.
Origin	Chemical Concepts
NIST MS number	151727

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References

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]

McCullough, Messerly, et al., 1963, 2
McCullough, J.P.; Messerly, J.F.; Moore, R.T.; Todd, S.S., J. Phys. Chem., 1963, 67, 677. [all data]

Fulem, Ruzicka, et al., 2003
Fulem, M.; Ruzicka, K.; Ruzicka, V.; Hulicius, E.; Simecek, T.; Melichar, K.; Pangrác, J.; Rushworth, S.A.; Smith, L.M., Vapor pressure of metal organic precursors, Journal of Crystal Growth, 2003, 248, 99-107, https://doi.org/10.1016/S0022-0248(02)01840-7 . [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]

den Berg, Ingemann, et al., 1992
den Berg, K.J. van; Ingemann, S.; Nibbering, N.M.M., Gas Phase Reactions of Negative Ions with Trimethylaluminum: Formation and Reactivity of the Me3AlH- Ion., Org. Mass Spectrom., 1992, 27, 4, 523, https://doi.org/10.1002/oms.1210270427 . [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

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
T_triple	Triple point temperature
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
Δ_fusH	Enthalpy of fusion
Δ_fusS	Entropy of fusion
Δ_rH°	Enthalpy of reaction at standard conditions
Δ_rS°	Entropy of reaction at standard conditions
Δ_subH	Enthalpy of sublimation
Δ_vapH	Enthalpy of vaporization
Δ_vapH°	Enthalpy of vaporization at standard conditions

Data from NIST Standard Reference Database 69: NIST Chemistry WebBook
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