The question of quadruple bonding in C2 has emerged as a hot button issue, with opinions sharply divided between the practitioners of Valence Bond (VB) and Molecular Orbital (MO) theory.
Metal-free
catalysis by sterically encumbered Lewis Acid–Base pairs, popularly
known as frustrated Lewis pairs (FLPs), is gaining importance
by the day due to its promise of providing a greener alternative to
transition-metal-based catalysis. One of the stumbling blocks in achieving
catalytic dehydrogenation of amine-boranes is catalyst deactivation
by the reaction product. Herein, we have theoretically investigated
the routes of a dimethylxanthene-derived B,P-FLP-catalyzed
dehydrogenation of dimethylamine-borane (DMAB), a rare
instance which avoids catalyst inhibition by the reaction product.
Our computational findings reveal that the dehydrogenation proceeds
via formation of the ion pair [FLP-H]
–
and [HMe
2
N-BH
2
-H-BH
2
-NMe
2
H]
+. This step is followed by indirect B–H activation assisted
by a second DMAB molecule and further H2 release
via deprotonation by the PPh2 center. It is revealed that
the binding of NMe
2
BH
2
to the FLP is unfavorable
which ensures smooth propagation of the catalytic cycle. Catalytic
dehydrogenation by the same mechanistic pathway is somewhat inhibited
in the case of ammonia-borane by the same FLP due to
the latent stabilization provided by strong hydrogen bonding interaction
to FLP-NH
2
BH
2
adduct which renders partial deactivation of
the catalyst.
Hydrogen Storage is an indispensable component of hydrogen based fuel economy. Chemical hydrogen storage relies on development of lightweight compounds which can deliver high weight percentage of H2 at moderate...
Background: Supraglottic airway devices (SADs) such as LMA classic (cLMA), I-Gel, etc. are indispensable tool for the anaesthesiologists experienced in airway management. But studies evaluating the performance of these devices in the hands of unskilled personnel are scarce.
Aims and Objective: To determine the procedure time and the proportion of patients having successful placement of I-gel and LMA classic by first-year Post Graduate Trainees (PGTs) of Anaesthesiology who tried insertion of those devices after a short training in mannequins without any hands-on training regarding placement of the devices in human.
Materials and Methods: After getting Institute’s Ethics Committee’s approval for this interventional study, forty adult patients, posted for short surgical or gynaecological surgery, were randomly allocated in to two groups to have placement of either I-Gel (group ‘I’, n=20) or cLMA (group ‘C’, n=20) by first-year PGTs. The procedure time (Primary outcome) i.e. the time taken for successful placement of either device was determined and compared. A standard technique of anaesthesia was followed in every patient. Any adverse event such as sore throat, odynophagia, blood stain on the device, etc. was also recorded.
Results: All patients were comparable with respect to demographic data and Mallampati scores. The mean procedure time (seconds) was considerably lower in I-Gel group compared with cLMA (63.3 ± 57.2 versus 163.0 ± 158.3, respectively, P value <0.001). The incidence of successful placement at first attempt was significantly higher for I-Gel group. The incidence of adverse events was comparable.
Conclusion: Procedure time for I-Gel insertion is significantly shorter than with LMA Classic along with a higher success rate with first attempt for the former. I-Gel may be a better alternative as airway device for the unskilled anaesthesiologist.
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