Catalysis by Acids and Bases

<div>The isolation and reactivities of two pentacoordinated phosphorus–tetracoordinated boron bonded compounds were</div><div>explored. A strong Lewis acidic boron reagent and electron-withdrawing ligand system were required to form the</div><div>pentacoordinated phosphorus state of the P–B bond. The first compound, a phosphoranyl-trihydroborate, gave a THF</div><div>stabilised phosphoranyl-borane intermediate upon a single hydride abstraction in THF. This compound could undergo a</div><div>unique rearrangement reaction, that involved a two-fold ring expansion, to give an unusual fused bicyclic compound or it</div><div>could act as a mono-hydroboration reagent. The hydroboration reactivity of the intermediate was found to be more reactive</div><div>towards alkynes over alkenes with good to moderate regioselectivity towards the terminal carbon. The second compound,</div><div>a phosphoranyl-triarylborate, was found to have a vastly different reactivity to the trihydroborate as it was highly stable</div><div>towards acids and bases. This is thought to be due to the large bulk around the P–B bond as shown in the crystal structure</div>

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Use of a sequencing batch biofilter for degradation of azo dyes (acids and bases)

Water Science & Technology ◽

10.2166/wst.2000.0532 ◽

2000 ◽

Vol 42 (5-6) ◽

pp. 329-336 ◽

Cited By ~ 8

Author(s):

M. Quezada ◽

I. Linares ◽

G. Buitrón

Keyword(s):

Azo Dyes ◽

Azo Dye ◽

Degradation Rate ◽

Removal Rate ◽

Textile Effluent ◽

Colour Removal ◽

Substrate Degradation ◽

Acids And Bases ◽

Removal Efficiencies ◽

Basic Red 46

The degradation of azo dyes in an aerobic biofilter operated in an SBR system was studied. The azo dyes studied were Acid Red 151 and a textile effluent containing basic dyes (Basic Blue 41, Basic Red 46 and 16 and Basic Yellow 28 and 19). In the case of Acid Red 151 a maximal substrate degradation rate of 288 mg AR 151/lliquid·d was obtained and degradation efficiencies were between 60 and 99%. Mineralization studies showed that 73% (as carbon) of the initial azo dye was transformed to CO2 by the consortia. The textile effluent was efficiently biodegraded by the reactor. A maximal removal rate of 2.3 kg COD/lliquid·d was obtained with removal efficiencies (as COD) varying from 76 to 97%. In all the cycles the system presented 80% of colour removal.

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Acids, bases and buffer solutions

10.1093/oso/9780198782957.003.0017 ◽

2018 ◽

Author(s):

Dennis Sherwood ◽

Paul Dalby

Keyword(s):

First Principles ◽

Buffer Capacity ◽

Unique Feature ◽

Dissociation Constants ◽

Equilibrium Composition ◽

Buffer Solutions ◽

Acid And Base ◽

Water Ph ◽

Acids And Bases ◽

Conjugate Bases

Many reactions in solution involve acids and bases, and so this chapter examines these important reactions in detail. Topics covered include the ionisation of water, pH, pOH, acids and bases, conjugate acids and conjugate bases, acid and base dissociation constants, the Henderson-Hasselbalch equation, the Henderson-Hasselbalch approximation, buffer solutions and buffer capacity. A unique feature of this chapter is a ‘first principles’ analysis of how a reaction buffered at a particular pH achieves an equilibrium composition different from that of the same reaction taking place in an unbuffered solution. This introduces some concepts which are important in understanding the biochemical standard state, as required for Chapter 23.

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