Phosphorus pentabromide

Phosphorus pentabromide is a reactive, yellow solid of formula PBr₅, which has the structure PBr₄⁺Br⁻ in the solid state but in the vapor phase is completely dissociated to PBr₃ and Br₂. Rapid cooling of this phase to 15 K leads to formation of the ionic species [PBr₄]⁺[Br₃]⁻.

It can be used in organic chemistry to convert carboxylic acids to acyl bromides. It is highly corrosive. It decomposes above 100 °C to give phosphorus tribromide and bromine:

Reversing this equilibrium to generate PBr₅ by addition of Br₂ to PBr₃ is difficult in practice because the product is susceptible to further addition to yield PBr₇.

References

Phosphorus tribromide

Phosphorus tribromide is a colourless liquid with the formula PBr₃. It is a colourless liquid that fumes in moist air due to hydrolysis and has a penetrating odour. It is used in the laboratory for the conversion of alcohols to alkyl bromides.

Preparation

PBr₃ is prepared by treating red phosphorus with bromine. An excess of phosphorus is used in order to prevent formation of PBr₅:

Because the reaction is highly exothermic, it is often conducted in the presence of a diluent such as PBr₃.

Reactions

Phosphorus tribromide, like PCl₃ and PF₃, has both properties of a Lewis base and a Lewis acid. For example, with a Lewis acid such as boron tribromide it forms stable 1 :1 adducts such as Br₃B · PBr₃. At the same time PBr₃ can react as an electrophile or Lewis acid in many of its reactions, for example with amines.

The most important reaction of PBr₃ is with alcohols, where it replaces an OH group with a bromine atom to produce an alkyl bromide. All three bromides can be transferred.

Phosphorus heptabromide

Phosphorus heptabromide is an inorganic compound with the formula PBr₇. It is one of the phosphorus bromides. At normal conditions, it forms red prismatic crystals. PBr₇ can be prepared by the sublimation of a mixture of phosphorus pentabromide and bromine.

The structure consists of the PBr₄⁺ cation paired with a tribromide (Br₃⁻) anion.

See also

References

PBR&B

PBR&B, also referred to as R-Neg-B, hipster R&B, electronic R&B, indie R&B and alternative R&B, is a term used by music journalists to describe an emerging, stylistic alternative to contemporary R&B.

Etymology

PBR&B is a portmanteau of PBR (the abbreviation for Pabst Blue Ribbon, a beer most recently associated with the hipster subculture) and R&B. However, despite being the most widely used names for the genre, these terms are often criticized for "pigeonholing" artists into hipster subculture and are derisive.Slate suggests the name "R-Neg-B". Others suggest that it falls into a broad category of "alternative R&B" or "indie R&B".

The genre has sometimes been called "noir&B."

The first use of the term "PBR&B" was on Twitter by Sound of the City writer Eric Harvey on a March 22, 2011 post. Three years later, amazed and distressed at how far the term—meant as a joke—had traveled, Harvey wrote an extensive essay about it for Pitchfork.

Characteristics

Recording artists associated with the term include , The Weeknd, Bryson Tiller, Sean Christopher, Autre Ne Veut, Jessy Lanza, Banks, FKA twigs, Tinashe, How to dress well, Kenna, Solange, Miguel, PartyNextDoor,Jhené Aiko,Janelle Monáe,Kelela,Danny! and James Blake. Barry Walters of Spin characterizes their unconventional style as an "exchange between EDM, rock, hip hop and R&B's commercial avant-garde", and cites The Weeknd's Beauty Behind the Madness and Thursday, Miguel's Kaleidoscope Dream, Kelela's hallucinogen, Holy Other's With U, Drake's Take Care and Kenna's Make Sure They See My Face as works associated with PBR&B. Brandon Neasman of The Grio observes a "changing of the guard in R&B, from the smooth, cool heartthrobs to these vulnerable, off-kilter personalities" amid the prevalence of social media in society. Neasman finds the subject matter of "these new-wave artists" to be more "relatable" and writes of its characteristics: