Propanal, 2-methyl-

Formula: C₄H₈O
Molecular weight: 72.1057
IUPAC Standard InChI: InChI=1S/C4H8O/c1-4(2)3-5/h3-4H,1-2H3
IUPAC Standard InChIKey: AMIMRNSIRUDHCM-UHFFFAOYSA-N
CAS Registry Number: 78-84-2
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: Isobutyraldehyde; α-Methylpropionaldehyde; Isobutanal; Isopropylaldehyde; Isopropylformaldehyde; 2-Methylpropanal; 2-Methylpropionaldehyde; iso-C3H7CHO; Isobutylaldehyde; Isobutyric aldehyde; 2-Methyl-1-propanal; Isobutyraldehyd; Propionaldehyde, 2-methyl-; Valine aldehyde; Isobutaldehyde; Isobutyryl aldehyde; Methyl propanal; NCI-C60968; UN 2045; Isobutyral; NSC 6739; 2-methylpropanal (isobutanal)
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Gas phase thermochemistry data

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Data compiled as indicated in comments:
ALS - Hussein Y. Afeefy, Joel F. Liebman, and Stephen E. Stein
DRB - Donald R. Burgess, Jr.

Quantity	Value	Units	Method	Reference	Comment
Δ_fH°_gas	-51.57 ± 0.37	kcal/mol	Cm	Wiberg, Crocker, et al., 1991	ALS
Δ_fH°_gas	-51.72	kcal/mol	N/A	Gubareva and Gerasimov, 1990	Value computed using Δ_fH_liquid° value of -247.9±0.7 kj/mol from Gubareva and Gerasimov, 1990 and Δ_vapH° value of 31.5 kj/mol from Connett, 1975.; DRB
Δ_fH°_gas	-51.55 ± 0.31	kcal/mol	Eqk	Connett, 1975	Heat of dehydrogenation; ALS
Δ_fH°_gas	-52.1	kcal/mol	Ccb	Tjebbes, 1962	ALS

Condensed phase thermochemistry data

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Data compiled by: Hussein Y. Afeefy, Joel F. Liebman, and Stephen E. Stein

Quantity	Value	Units	Method	Reference	Comment
Δ_fH°_liquid	-59.11 ± 0.22	kcal/mol	Cm	Wiberg, Crocker, et al., 1991
Δ_fH°_liquid	-59.2 ± 0.2	kcal/mol	Ccb	Gubareva and Gerasimov, 1990
Δ_fH°_liquid	-59.08 ± 0.31	kcal/mol	Eqk	Connett, 1975	Heat of dehydrogenation
Δ_fH°_liquid	-59.81 ± 0.18	kcal/mol	Ccb	Tjebbes, 1962
Quantity	Value	Units	Method	Reference	Comment
Δ_cH°_liquid	-590.2 ± 0.2	kcal/mol	Ccb	Gubareva and Gerasimov, 1990	Corresponding Δ_fHº_liquid = -59.27 kcal/mol (simple calculation by NIST; no Washburn corrections)
Δ_cH°_liquid	-589.67 ± 0.18	kcal/mol	Ccb	Tjebbes, 1962	Corresponding Δ_fHº_liquid = -59.79 kcal/mol (simple calculation by NIST; no Washburn corrections)

Phase change data

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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
DRB - Donald R. Burgess, Jr.
ALS - Hussein Y. Afeefy, Joel F. Liebman, and Stephen E. Stein

Quantity	Value	Units	Method	Reference	Comment
T_boil	336. ± 2.	K	AVG	N/A	Average of 24 out of 27 values; Individual data points
Quantity	Value	Units	Method	Reference	Comment
T_fus	201.00	K	N/A	Tjebbes, 1962, 2	Uncertainty assigned by TRC = 0.5 K; TRC
T_fus	207.3	K	N/A	Anonymous, 1958	Uncertainty assigned by TRC = 2. K; TRC
T_fus	145.	K	N/A	Cook, 1952	Uncertainty assigned by TRC = 3. K; TRC
T_fus	207.3	K	N/A	Timmermans, 1922	Uncertainty assigned by TRC = 0.4 K; TRC
Quantity	Value	Units	Method	Reference	Comment
Δ_vapH°	7.6 ± 0.2	kcal/mol	AVG	N/A	Average of 7 values; Individual data points

Enthalpy of vaporization

Δ_vapH (kcal/mol)	Temperature (K)	Method	Reference	Comment
7.50	318.	N/A	Eng and Sandler, 1984	Based on data from 313. to 324. K.; AC
7.60	324.	N/A	Brazhnikov, Peshchenko, et al., 1976	Based on data from 309. to 337. K.; AC
7.98	340.	EB	Wojtasinski, 1963	Based on data from 333. to 347. 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
286.08 to 336.00	3.86824	1060.141	-63.196	Seprakova, Paulech, et al., 1959	Coefficents calculated by NIST from author's data.

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:

Gas phase ion energetics data

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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 C₄H₈O⁺ (ion structure unspecified)

Quantity	Value	Units	Method	Reference	Comment
IE (evaluated)	9.71 ± 0.02	eV	N/A	N/A	L
Quantity	Value	Units	Method	Reference	Comment
Proton affinity (review)	190.6	kcal/mol	N/A	Hunter and Lias, 1998	HL
Quantity	Value	Units	Method	Reference	Comment
Gas basicity	183.0	kcal/mol	N/A	Hunter and Lias, 1998	HL

Ionization energy determinations

IE (eV)	Method	Reference	Comment
9.72	PI	Traeger and McAdoo, 1986	LBLHLM
9.705 ± 0.005	PE	Hernandez, Masclet, et al., 1977	LLK
9.69 ± 0.01	PE	Cocksey, Eland, et al., 1971	LLK
9.74 ± 0.03	PI	Watanabe, Nakayama, et al., 1962	RDSH
9.82	PE	Tam, Yee, et al., 1974	Vertical value; LLK

Appearance energy determinations

Ion	AE (eV)	Other Products	Method	Reference	Comment
C₂H₃O⁺	10.29	C₂H₅	PI	Traeger and McAdoo, 1986	LBLHLM

De-protonation reactions

C₄H₇O^- + = Propanal, 2-methyl-

By formula: C₄H₇O^- + H⁺ = C₄H₈O

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	366.8 ± 3.0	kcal/mol	D-EA	Alconcel, Deyerl, et al., 2001	gas phase; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	359.5 ± 3.1	kcal/mol	H-TS	Alconcel, Deyerl, et al., 2001	gas phase; B

References

Go To: Top, Gas phase thermochemistry data, Condensed phase thermochemistry data, Phase change data, Gas phase ion energetics data, Notes

Wiberg, Crocker, et al., 1991
Wiberg, K.B.; Crocker, L.S.; Morgan, K.M., Thermochemical studies of carbonyl compounds. 5. Enthalpies of reduction of carbonyl groups, J. Am. Chem. Soc., 1991, 113, 3447-3450. [all data]

Gubareva and Gerasimov, 1990
Gubareva, A.I.; Gerasimov, P.A., Physicochemical properties of isobutyraldehyde, J. Appl. Chem. USSR, 1990, 63, 844-846. [all data]

Connett, 1975
Connett, J.E., Chemical equilibria 6. Measurement of equilibrium constants for the dehydrogenation of 2-methylpropan-1-ol by a vapour-flow technique, J. Chem. Thermodyn., 1975, 7, 1159-1162. [all data]

Tjebbes, 1962
Tjebbes, J., Heats of combustion of propanal and 2-methyl propanal, Acta Chem. Scand., 1962, 16, 953-857. [all data]

Tjebbes, 1962, 2
Tjebbes, J., Acta Chem. Scand., 1962, 16, 953. [all data]

Anonymous, 1958
Anonymous, R., , Am. Pet. Inst. Res. Proj. 45, Ohio State Univ., 1958. [all data]

Cook, 1952
Cook, N.C., , Unpublished, Final Rep. Stand. Proj. on Oxygenated Compounds, Penn. State Univ., College Park, PA, 1952. [all data]

Timmermans, 1922
Timmermans, J., Investigation of the Freezing Point of Organic Substances VII, Bull. Soc. Chim. Belg., 1922, 31, 389. [all data]

Eng and Sandler, 1984
Eng, Robert; Sandler, Stanley I., Vapor-liquid equilibria for three aldehyde/hydrocarbon mixtures, J. Chem. Eng. Data, 1984, 29, 2, 156-161, https://doi.org/10.1021/je00036a017 . [all data]

Brazhnikov, Peshchenko, et al., 1976
Brazhnikov, M.M.; Peshchenko, A.D.; Ral'ko, O.V., Zh. Prikl. Khim. (Leningrad), 1976, 49, 1041. [all data]

Wojtasinski, 1963
Wojtasinski, Jerome G., Measurement of Total Pressures for Determining Liquid-Vapor Equilibrium Relations of the Binary System Isobutyraldehyde n-Butyraldehyde., J. Chem. Eng. Data, 1963, 8, 3, 381-385, https://doi.org/10.1021/je60018a028 . [all data]

Seprakova, Paulech, et al., 1959
Seprakova, M.; Paulech, J.; Dykyj, J., Dampfdruck der Butyraldehyde, Chem. Zvesti, 1959, 13, 313-316. [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]

Traeger and McAdoo, 1986
Traeger, J.C.; McAdoo, D.J., Decomposition thresholds and associated translational energy releases for eight C₄H₈O⁺ isomers, Int. J. Mass Spectrom. Ion Processes, 1986, 68, 35. [all data]

Hernandez, Masclet, et al., 1977
Hernandez, R.; Masclet, P.; Mouvier, G., Spectroscopie de photoelectrons d'aldehydes et de cetones aliphatiques, J. Electron Spectrosc. Relat. Phenom., 1977, 10, 333. [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]

Watanabe, Nakayama, et al., 1962
Watanabe, K.; Nakayama, T.; Mottl, J., Ionization potentials of some molecules, J. Quant. Spectry. Radiative Transfer, 1962, 2, 369. [all data]

Tam, Yee, et al., 1974
Tam, W.-C.; Yee, D.; Brion, C.E., Photoelectron spectra of some aldehydes and ketones, J. Electron Spectrosc. Relat. Phenom., 1974, 4, 77. [all data]

Alconcel, Deyerl, et al., 2001
Alconcel, L.S.; Deyerl, H.J.; Continetti, R.E., Effects of alkyl substitution on the energetics of enolate anions and radicals, J. Am. Chem. Soc., 2001, 123, 50, 12675-12681, https://doi.org/10.1021/ja0120431 . [all data]

Notes

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Symbols used in this document:

AE	Appearance energy
IE (evaluated)	Recommended ionization energy
T_boil	Boiling point
T_fus	Fusion (melting) point
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_rG°	Free energy of reaction at standard conditions
Δ_rH°	Enthalpy of reaction at standard conditions
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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