Rhodium-catalyzed asymmetric conjugate addition to R,âunsaturated ketones and related compounds is now well-recognized to be one of the most efficient methods of introducing aryl and alkenyl groups with high enantioselectivity.1 On the other hand, asymmetric conjugate addition of alkynyl groups has not been welldeveloped in spite of its high synthetic utility.2 A most straightforward and conven...

The entrance channel leading to the addition reaction between the hydroxyl radical and acetylene has been examined by spectroscopic characterization of the asymmetric CH stretching band of the pi-hydrogen bonded OH-acetylene reactant complex. The infrared action spectrum observed at 3278.6 cm(-1) (origin) consists of seven peaks of various intensities and widths, and is very different from thos...

Over the past 50 years, numerous roads towards carbon-based materials have been explored, all of them being paved using mainly one functional group as the brick: acetylene. The acetylene group, or the carbon-carbon triple bond, is one of the oldest and simplest functional groups in chemistry, and although not present in any of the naturally occurring carbon allotropes, it is an essential tool t...

The effect of acetylene ((14)C(2)H(2)) on aerobic and anaerobic ammonia oxidation by Nitrosomonas eutropha was investigated. Ammonia monooxygenase (AMO) was inhibited and a 27 kDa polypeptide (AmoA) was labelled during aerobic ammonia oxidation. In contrast, anaerobic, NO(2)-dependent ammonia oxidation (NO(2)/N(2)O(4) as oxidant) was not affected by acetylene. Further studies gave evidence that...

Non-linear rates of acetylene reduction and concomitant H2 evolution were observed for the nitrogenase of Klebsiella pneumoniae at 10 degrees C. A lag phase of 1-4 min, dependent on the ratio of Mo-Fe protein to Fe protein present, occurred before linear rates of acetylene reduction were achieved. A complementary burst phase for concomitant H2 evolution in the presence of acetylene was also obs...

Examination of root systems and adhering soil associated with unusually green corn plants from nitrogen-deficient areas in fields has revealed higher acetylene-reducing activities than comparable root systems of chlorotic plants that appeared to be nitrogen deficient. From the root systems with acetylene-reducing activity, N(2)-fixing Enterobacter cloacae were isolated. Pure cultures of the org...

Co-adsorbed acetylene and hydrogen react on Pd(l l l ) to form ethylene and butene. Benzene is also formed and it is found that the low temperature (~ 280 K) desorption state observed on the clean surface is virtually unaffected by the presence of hydrogen whereas the higher temperature (~ 520 K) state is modified. However, adsorbing benzene onto a hydrogen pre-covered surface just affects the ...

Acetylene is a slow-binding inhibitor of the Ni- and Fe-containing dimeric hydrogenase isolated from Azotobacter vinelandii. Acetylene was released from hydrogenase during the recovery from inhibition. This indicates that no transformation of acetylene to another compound occurred as a result of the interaction with hydrogenase. However, the release of C2H2 proceeds more rapidly than the recove...

A new and extremely sensitive method for measuring nitrogenase activity through acetylene reduction is presented. Ethylene produced by nitrogenase-mediated reduction of acetylene is detected by using laser photoacoustics (LPA). This method possesses a detection limit making it 3 orders of magnitude more sensitive than traditional gas chromatographic analysis. Photoacoustic detection is based on...

The proton resonance spectra of a number of acetylenes of fixed geometry were recorded in dilute CDCl3 solution and assigned. These were acetylene, equatorialand axial-cyclohexylacetylene at 60 C, 1,4-di-1-adamantylbutadiyne, 1-ethynyl-tand -c-4-tert-butylcyclohexan-r-1-ol, 2-exo-ethynylnorbornan-2-ol† and 2,2 -ethyne-1,2diyldibornan-2-ol. The aromatic acetylenes measured were phenylacetylene, ...