Donald F. McMillen

Bio: Donald F. McMillen is an academic researcher from SRI International. The author has contributed to research in topics: Carbochemistry & Thermal decomposition. The author has an hindex of 18, co-authored 43 publications receiving 2737 citations.

Hydrocarbon Bond Dissociation Energies

Abstract: The best available values for homolytic bond dissociation energies (BDEs) of various classes of neutral compounds are considered in this review. (BDEs in ionic species is a legitimate subject that is touched on briefly and could easily be included in a longer review. The same can be said for heterolytic BDEs, which are not reviewed as such, although some of the ionic thermochemical data discussed yield values for these processes.) The major emphasis is on hydrocarbons and their nitrogen, oxygen, sulfur, halogen, and silicon-containing derivations, but limited data for inorganic molecules are included. The focus is particularly on prototypical radicals whose heats of formation, formerly thought to be well in hand, have recently been called into serious question. The intent is to include all the major types of sigma bonds, if not all specific cases where known or estimatable heats of formation allow bond dissociation energies to be generated. This review attempts to acknowledge all the standard techniques for measuring BDEs in polyatomic molecules and to offer critical analysis of selected portions of the literature. This leaves values that the authors recommend as the most likely to be correct at the time of this writing. 246 references, 9 tables.

Mechanism of decomposition of nitroaromatics. Laser-powered homogeneous pyrolysis of substituted nitrobenzenes

Abstract: Laser-powered homogeneous pyrolysis (LPHP) has been used to study the gas-phase thermal decomposition of nitrobenzene (NB), m-dinitrobenzene (m-DNB), p-nitrotoluene (p-NT), o-nitrotoluene (o-NT), and 2,4-dinitrotoluene (2,4-DNT) under conditions where surface-catalyzed reactions are precluded. The Arrhenius parameters have been determined by comparative rate measurements relative to cyclohexene decomposition and the reaction mechanisms have been established. In all cases, the rate-limiting step is the homolysis of the Ar-NO2 bond. The measured Arrhenius parameters for homolysis range from log A = 14.5 to 16.4 and E/sub a/ from 67.0 to 70.0 kcal/mol. The c-NO2 bond dissociation energies (kcal/mol) and values of log k (s ) for NB, m-DNB, p-NT, o-NT, and 2,4-DNT have been derived from these results and are as follows: 71.4 +/- 2.0, (15.5 +/- 0.5) - (68.2 +/- 1.7)/2.3RT; 73.2 +/- 2.4, (14.5 +/- 0.5) - (70.0 +/- 2.1)/2.3RT; 71.4 +/- 2.3, (14.9 +/- 0.5) - (68.2 +/- 2.0)/2.3RT; 70.2 +/- 2.5, (16.4 +/- 0.6) - (67.0 +/- 2.2)/2.3RT; 70.6 +/- 2.0, (15.3 +/- 0.4) - (67.4 +/- 1.7)/2.3RT. 15 references, 6 figures, 4 tables.

The thermal decomposition of the new energetic material ammoniumdinitramide (NH4N(NO2)2) in relation to Nitramide (NH2NO2) and NH4NO3

Abstract: This qualitative study examines the response of the novel energetic material ammonium dinitramide (ADN), NH4N(NO2)2, to thermal stress under low heating rate conditions in a new experimental apparatus. It involved a combination of residual gas mass spectrometry and FTIR absorption spectroscopy of a thin cryogenic condensate film resulting from deposition of ADN pyrolysis products on a KCl window. The results of ADN pyrolysis were compared under similar conditions with the behavior of NH4NO3 and NH2NO2 (nitramide), which served as reference materials. NH4NO3 decomposes into HNO3 and NH3 at 182°C and is regenerated on the cold cryostat surface. HNO3 undergoes presumably heterogeneous loss to a minor extent such that the condensed film of NH4NO3 contains occluded NH3. Nitramide undergoes efficient heterogeneous decomposition to N2O and H2O even at ambient temperature so that pyrolysis experiments at higher temperatures were not possible. However, the presence of nitramide can be monitored by mass spectrometry at its molecular ion (m/ℯ 62). ADN pyrolysis is dominated by decomposition into NH3 and HN(NO2)2 (HDN) in analogy to NH4NO3, with a maximum rate of decomposition under our conditions at approximately 155°C. The two vapor phase components regenerate ADN on the cold cryostat surface in addition to deposition of the pure acid HDN and H2O. Condensed phase HDN is found to be stable for indefinite periods of time at ambient temperature and vacuum conditions, whereas fast heterogeneous decomposition of HDN at higher temperature leads to N2O and HNO3. The HNO3 then undergoes fast (heterogeneous) decomposition in some experiments. Gas phase HDN also undergoes fast heterogeneous decomposition to NO and other products, probably on the internal surface (ca. 60°C) of the vacuum chamber before mass spectrometric detection. © 1993 John Wiley & Sons, Inc.

Thermal, Catalytic, Regiospecific Functionalization of Alkanes

Abstract: The formation of a single product from terminal functionalization of linear alkanes from a transition metal-catalyzed reaction is reported. The rhodium complex Cp*Rh(eta(4)-C(6)Me(6)) (Cp*, C(5)Me(5); Me, methyl) catalyzes the high-yield formation of linear alkylboranes from commercially available borane reagents under thermal conditions. These reactions now allow catalytic, regiospecific functionalization of alkanes under thermal conditions. The organoborane products are among the most versatile synthetic intermediates in chemistry and serve as convenient precursors to alcohols, amines, and other common classes of functionalized molecules.