In chemistry, an enantiomer is one of two stereoisomers that are mirror images of each other that are non-superposable, much as one's left and right hands are mirror images of each other that cannot appear identical by reorientation. A single chiral atom or similar structural feature in a compound causes that compound to have two possible structures which are non-superposable, each a mirror image of the other; each member of the pair is termed an enantiomorph. The presence of multiple chiral features in a given compound increases the number of geometric forms possible, though there may still be some perfect-mirror-image pairs. A sample of a chemical is considered enantiopure when it has, within the limits of detection, molecules of only one chirality; when present in a symmetric environment, enantiomers have identical chemical and physical properties except for their ability to rotate plane-polarized light by equal amounts but in opposite directions. Such compounds are therefore described as optically active, with specific terms for each enantiomer based on the direction: a dextrorotatory compound rotates light a clockwise direction whereas a levorotatory compound rotates light in a counter-clockwise direction.
A mixture of equal number of both enantiomers is called a racemate. In a racemic mixture, the amount of positive rotation is counteracted by the equal amount of negative rotation, so the net rotation is zero. For all intents and purposes, pairs of enantiomers have the same Gibbs free energy. However, theoretical physics predicts that due to parity violation of the weak nuclear force, there is a minute difference in energy between enantiomers due to the weak neutral current mechanism; this difference in energy is far smaller than energy changes caused by a trivial change in molecular conformation and far too small to measure by current technology, is therefore chemically inconsequential. Enantiomer members have different chemical reactions with other enantiomer substances. Since many biological molecules are enantiomers, there is sometimes a marked difference in the effects of two enantiomers on biological organisms. In drugs, for example only one of a drug's enantiomers is responsible for the desired physiological effects, while the other enantiomer is less active, inactive, or sometimes productive of adverse effects.
Owing to this discovery, drugs composed of only one enantiomer can be developed to make the drug work better and sometimes eliminate some side effects. An example is eszopiclone, just a single enantiomer of an older racemic drug called zopiclone. One enantiomer is responsible for all the desired effects, while the other enantiomer seems to be inactive, the so the dose of eszopiclone is half that of zopiclone. In chemical synthesis of enantiomeric substances, non-enantiomeric precursors produce racemic mixtures. In the absence of an effective enantiomeric environment, separation of a racemic mixture into its enantiomeric components is impossible, although certain racemic mixtures spontaneously crystallize in the form of a racemic conglomerate, in which crystals of the enantiomers are physically segregated and may be separated mechanically. However, most racemates will crystallize in crystals containing both enantiomers in a 1:1 ratio, arranged in a regular lattice; the R/S system is an important nomenclature system used to denote distinct enantiomers.
Another system is based on prefix notation for optical activity: - and - or d- and l-. The Latin words for left are laevus and sinister, the word for right is dexter; the English word right is a cognate of rectus. This is the origin of the L/D and S/R notations, the employment of prefixes levo- and dextro- in common names. An asymmetric carbon atom is one which has bonds with four different atoms or groups, so that these bonds can be arranged in two different ways which are not superposable. Most compounds that contain one or more asymmetric carbon atoms show enantiomerism, but this is not always true. Compounds that contain two or more asymmetric carbon atoms but have a plane of symmetry with respect to the whole molecule are known as meso compounds. A meso compound does not have a mirror image stereoisomer. For instance, meso tartaric acid has two asymmetric carbon atoms, but it does not exhibit enantiomerism because each of the two halves of the molecule is equal and opposite to the other and thus is superposable on its geometric mirror image.
Conversely, there exist forms of chirality. In fact, there are four distinct types of chirality: central, axial and helical chirality. Having an enantiomer by virtue of an asymmetric carbon atom represents the most common type of central chirality; the other three types of chirality do not involve asymmetric carbon atoms, central chirality does not require the center of chirality to b
A chip race is an event that takes place in poker tournaments those with an escalating blinds, in which chips of denominations that are no longer needed are removed from play. This has the effect of reducing the number of physical chips in front of any player, makes it easier for the players to count their stacks and their bets. In a typical chip race: All players color up their lesser-valued chips into greater denominations. For example, if the blinds have increased to a level where $5 chips are no longer needed to post blinds, each five $5 chips will be exchanged for a $25 chip. Players will temporarily keep any leftover chips that cannot be colored up to larger chips. All leftover chips are counted, equivalent chips in the larger denomination are presented to the table. Continuing the example, if there are 15 $5 chips remaining among 6 players, 3 $25 chips are prepared. In the event the remaining smaller chips do not add up to a whole larger chip, an extra larger chip should be added as long as the leftover smaller chips total at least half a single larger chip.
Each player with leftover chips in the smaller denomination will receive one card for each chip. The cards are dealt face up, starting from seat one, to the dealer's left; each player due to receive cards will receive all of his cards before the next player, rather than a "traditional" card deal. The larger chips are issued to the players with the highest single cards showing. No player is issued more than one chip. Ties are broken by suit, using the same bridge order of the suits: Spades are highest, followed by Hearts and Clubs. All remaining lesser-value chips are removed from play. A chip race cannot eliminate a player from the game. In the event a player's last smaller-denomination chips are removed from play as part of the chip race, he automatically gets one chip of the lowest value still in play. To make it easier to manage the chip race, it is advised that one player at the table buys up all the smaller chips from the other player's stacks and exchanges them with chips of equal value in higher denomination.
Having all the chips in one stack makes it easier to count up and exchange
It's Our Thing is the sixth album released by The Isley Brothers on their own T-Neck Records imprint on April 26, 1969. Emancipated from three and a half years in Motown Records and encouraged by their international success in England, the Isleys composed this album in the style of Sly & the Family Stone/James Brown funk, dominating the music industry at the time but with their own flair as explained in their smash "It's Your Thing". Other hits off the album though it didn't chart included "I Know Who You Been Socking It To" and "Give the Women What They Want"; this album was the Isleys' first Top 40 record reaching #22 on the pop albums chart. Curiously, despite its importance in the career of the seminal group, this album was not released in CD format until 2008; the album was remastered and expanded for inclusion in the 2015 released CD box set "The RCA Victor & T-Neck Album Masters, 1959-1983". All tracks are written by O'Kelly Isley and Ronald Isley; the Isley BrothersRonald Isley – lead vocals O'Kelly Isley, Jr. and Rudolph Isley – background vocals Chris Jasper and Everett Collins – piano, keyboards Ernie Isley – bass, guitar Marvin Isley – basswithInstrumentation by assorted New York City musiciansTechnicalTony May – recording and mix engineer Acy R. Lehman – art direction James Kriegsmann Jr. – cover photography The Isley Brothers - It's Our Thing album review by Alex Henderson, credits & releases at AllMusic The Isley Brothers - It's Our Thing album releases & credits at Discogs The Isley Brothers - It's Our Thing album to be listened as stream on Spotify The Isley Brothers - It's Our Thing album back cover at www.