ABSTRACT
Anhydrous lanthanide(III) chlorides (Ln = Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb) react with 3 equiv of lithium 2,2,5,5-tetramethyl-2,5-disila-1-azacyclopentanide, Li[N[Si(CH3)2CH2Ch2Si(CH3)2]], in THF or Et(2)O to afford the monomeric four-coordinate heteroleptic ate complexes Ln[N[Si(CH3)2CH2CH2Si(CH3)2]]3(mu-Cl)Li(THF/Et2O)3 (Ln = Sm (1), Eu (2), Gd (3), Tb (4), Dy (5), Ho (6), Er (7), Tm (8), Yb (9)), whose solid-state structures were determined by the single-crystal X-ray diffraction technique. All complexes additionally were characterized by melting point determination, elemental analyses, and mass spectrometry.
ABSTRACT
This study establishes the rationale necessary for determining the time to change engine oil. This is based on identifying gaseous components in new and used automobile lubricants. Key compounds, so-called "signature", are separated and identified qualitatively by coupled gas chromatography/mass spectrometry. Volatile antioxidants at zero miles and fuel contaminants at low mileage are observed in the headspace of engine oil. Several oxidative degradation components have been positively identified in the used oil, which include the following: acetaldehyde, acetone, butanal, 2-propanol, acetic acid, 2-hexanol, benzoic acid, benzaldehyde, and 1-pentanol. This study strongly suggests that the status of lubricating oil can be determined by the analysis of the gas phase above the oil. Most importantly, it opens the possibility of performing conditional maintenance of the combustion engine based on information obtained from gas sensors.
ABSTRACT
A series of 21 secondary (alkyl)(trimethylsilyl)amines HNR(TMS) [R = n-propyl (1), i-propyl (2), n-butyl (3), i-butyl (4), s-butyl (5), tert-butyl (6), c-pentyl (7), n-pentyl (8), i-pentyl (9), l-methylbutyl (10), 2-methylbutyl (11), 1-ethylpropyl (12), 1,2-dimethylpropyl (13), tert-pentyl (14), phenyl (15), c-hexyl (16), n-hexyl (17), N,N-dimethyl-3-aminopropyl (18), benzyl (19), n-heptyl (20), 1,1,3,3-tert-butyl (21); TMS = Si(CH3)3] has been prepared and fully characterized by elemental analyses, multinuclear (1H, 13C, 29Si, 14N) NMR, IR, UV/vis, MS, and boiling point. A new method for determination of boiling points of milligram-size samples, based on DSC (differential scanning calorimetry), is described. Each amine has been converted to the corresponding zinc bis(amide) compound Zn[N(TMS)(R)]2 [R = n-propyl (22), i-propyl (23), n-butyl (24), i-butyl (25), s-butyl (26), tert-butyl (27), c-pentyl (28), n-pentyl (29), i-pentyl (30), 1-methylbutyl (31), 2-methylbutyl (32), 1-ethylpropyl (33), 1,2-dimethylpropyl (34), tert-pentyl (35), phenyl (36), c-hexyl (37), n-hexyl (38), N,N-dimethyl-3-aminopropyl (39), benzyl (40), n-heptyl (41), 1,1,3,3-tert-butyl (42); TMS = Si(CH3)3] and subsequently fully characterized by elemental analyses, multinuclear (1H, 13C, 29Si, 14N) NMR, IR, UV/vis, MS, and TGA. The experimental IR has been compared to the computationally calculated one for compound 27. Observed trends in volatility of the compounds are discussed in the context of the dominant intermolecular forces present in the condensed phase.
