Lewis acids and bases

Lewis acid is a chemical species that reacts with a Lewis base to form a Lewis adduct. A Lewis base, then, is any species that donates a pair of electrons to a Lewis acid to form a Lewis adduct. For example, OH⁻ and NH₃ are Lewis bases, because they can donate a lone pair of electrons. In the adduct, the Lewis acid and base share an electron pair furnished by the Lewis base. Usually the terms Lewis acid and Lewis base are defined within the context of a specific chemical reaction. For example, in the reaction of Me₃B and NH₃ to give Me₃BNH₃, Me₃B acts as a Lewis acid, and NH₃ acts as a Lewis base. Me₃BNH₃ is the Lewis adduct. The terminology refers to the contributions of Gilbert N. Lewis.

Depicting adducts

In many cases, the interaction between the Lewis base and Lewis acid in a complex is indicated by an arrow indicating the Lewis base donating electrons toward the Lewis acid using the notation of a dative bond—for example, Me₃B←NH₃. Some sources indicate the Lewis base with a pair of dots (the explicit electrons being donated), which allows consistent representation of from the base itself to the complex with the acid:

Lewis

Coordinates: 58°12′N 6°36′W / 58.2°N 6.6°W / 58.2; -6.6

Lewis (Scottish Gaelic: Leòdhas, pronounced [ʎɔː.əs̪], also Isle of Lewis) is the northern part of Lewis and Harris, the largest island of the Western Isles or Outer Hebrides (an archipelago) of Scotland. The total area of Lewis is 683 square miles (1,770 km²).

Lewis is, in general, the lower lying part of the island, with the other part, Harris, being more mountainous. The flatter, more fertile land means Lewis contains the largest settlement, Stornoway, and three-quarters of the population of the Western Isles. Beyond human habitation, the island's diverse habitats are home to an assortment of flora and fauna, such as the golden eagle, red deer and seals and are recognised in a number of conservation areas.

Lewis is of Presbyterian tradition with a rich history, having once been part of the Norse Kingdom of Mann and the Isles. Today, life is very different from elsewhere in Scotland with Sabbath observance, the Gaelic language and peat cutting retaining more importance than elsewhere. Lewis has a rich cultural heritage as can be seen from its myths and legends as well as the local literary and musical traditions.

Lewis (satellite)

Lewis was an American satellite which was to have been operated by NASA as part of the Small Satellite Technology Initiative. It carried two experimental Earth imaging instruments, and an ultraviolet astronomy payload. Due to a design flaw it failed within three days of reaching orbit, before it became operational.

Lewis was a 288 kilograms (635 lb) spacecraft, which was designed to operate for between one and three years. It was built by TRW under a contract which was signed on 11 July 1994. Its primary instruments were the Hyperspectral Imager, the Linear Etalon Imaging Spectral Array and the Ultraviolet Cosmic Background experiment. A number of technology demonstration payloads were also flown.

Launch

Lewis was launched by a LMLV-1 (Athena I) rocket flying from Space Launch Complex 6 at the Vandenberg Air Force Base. The launch was originally scheduled to take place in September 1996, but it was delayed due to technical problems affecting the rocket. Launch finally occurred at 06:51:01 GMT on 23 August 1997, and Lewis was successfully placed into a parking orbit with an apogee of 134 kilometres (83 mi), a perigee of 124 kilometres (77 mi), and 97.5 degrees of inclination. Lewis was to have raised itself into a higher orbit, at an altitude of 523 kilometres (325 mi).

M. Lewis (Surrey cricketer)

M. Lewis (dates unknown) was an English amateur cricketer who made two appearances in first-class cricket matches during the 1773 season.

Career

He was associated with Surrey.

References

External sources