SUMMARY / RELATED TOPICS

Aromaticity

In organic chemistry, aromaticity is a property of cyclic, planar structures with a ring of resonance bonds that gives increased stability compared to other geometric or connective arrangements with the same set of atoms. Aromatic molecules are stable, do not break apart to react with other substances. Organic compounds that are not aromatic are classified as aliphatic compounds—they might be cyclic, but only aromatic rings have special stability. Since the most common aromatic compounds are derivatives of benzene, the word aromatic refers informally to benzene derivatives, so it was first defined. Many non-benzene aromatic compounds exist. In living organisms, for example, the most common aromatic rings are the double-ringed bases in RNA and DNA. An aromatic functional group or other substituent is called an aryl group; the earliest use of the term aromatic was in an article by August Wilhelm Hofmann in 1855. Hofmann used the term for a class of benzene compounds, many of which have odors, unlike pure saturated hydrocarbons.

Aromaticity as a chemical property bears no general relationship with the olfactory properties of such compounds, although in 1855, before the structure of benzene or organic compounds was understood, chemists like Hofmann were beginning to understand that odiferous molecules from plants, such as terpenes, had chemical properties that we recognize today are similar to unsaturated petroleum hydrocarbons like benzene. In terms of the electronic nature of the molecule, aromaticity describes a conjugated system made of alternating single and double bonds in a ring; this configuration allows for the electrons in the molecule's pi system to be delocalized around the ring, increasing the molecule's stability. The molecule cannot be represented by one structure, but rather a resonance hybrid of different structures, such as with the two resonance structures of benzene; these molecules cannot be found in either one of these representations, with the longer single bonds in one location and the shorter double bond in another.

Rather, the molecule exhibits bond lengths in between those of double bonds. This seen model of aromatic rings, namely the idea that benzene was formed from a six-membered carbon ring with alternating single and double bonds, was developed by August Kekulé; the model for benzene consists of two resonance forms, which corresponds to the double and single bonds superimposing to produce six one-and-a-half bonds. Benzene is a more stable molecule than would be expected without accounting for charge delocalization; as it is a standard for resonance diagrams, the use of a double-headed arrow indicates that two structures are not distinct entities but hypothetical possibilities. Neither is an accurate representation of the actual compound, best represented by a hybrid of these structures. A C=C bond is shorter than a C−C bond. Benzene is a regular hexagon—it is planar and all six carbon–carbon bonds have the same length, intermediate between that of a single and that of a double bond. In a cyclic molecule with three alternating double bonds, the bond length of the single bond would be 1.54 Å and that of the double bond would be 1.34 Å.

However, in a molecule of benzene, the length of each of the bonds is 1.40 Å, indicating it to be the average of single and double bond. A better representation is that of the circular π-bond, in which the electron density is evenly distributed through a π-bond above and below the ring; this model more represents the location of electron density within the aromatic ring. The single bonds are formed from overlap of hybridized atomic sp2-orbitals in line between the carbon nuclei—these are called σ-bonds. Double bonds consist of a π-bond; the π-bonds are formed from overlap of atomic p-orbitals below the plane of the ring. The following diagram shows the positions of these p-orbitals: Since they are out of the plane of the atoms, these orbitals can interact with each other and become delocalized; this means that, instead of being tied to one atom of carbon, each electron is shared by all six in the ring. Thus, there are not enough electrons to form double bonds on all the carbon atoms, but the "extra" electrons strengthen all of the bonds on the ring equally.

The resulting molecular orbital is considered to have π symmetry. The first known use of the word "aromatic" as a chemical term—namely, to apply to compounds that contain the phenyl group—occurs in an article by August Wilhelm Hofmann in 1855. If this is indeed the earliest introduction of the term, it is curious that Hofmann says nothing about why he introduced an adjective indicating olfactory character to apply to a group of chemical substances only some of which have notable aromas. Many of the most odoriferous organic substances known are terpenes, which are not aromatic in the chemical sense, but terpenes and benzenoid substances do have a chemical characteristic in common, namely higher unsaturation than many aliphatic compounds, Hofmann may not have been making a distinction between the two categories. Many of the earliest-known examples of aromatic compounds, such as benzene and toluene, have distinctive pleasant smells; this property led to the term "aromatic" for this class of compounds, hence the term "aromaticity" for the discovered electronic property.

In the 19th century chemists found it puzzling that benzene could be so unreactive toward addition reactions, given its presumed high degree of unsaturation. The cyclohexatriene structure for benzene was first propo

William Wood (banker)

William Wood was a Scottish-American banker. Wood was born in Glasgow, Scotland on October 21, 1808, his father was a prominent Glasgow merchant and banker who could trace his lineage back to Admiral Sir Andrew Wood, a hero of the British Navy. At age 7, he went to William Angus' Grammar School in St Mungo for two years, followed by the Glasgow Grammar School and Dr. Duncan's School at Ruthwell. In October 1821, he entered The Glasgow Academy until age sixteen, when he matriculated at the University of St Andrews, where he took the second and third mathematical prizes. After St Andrews, he attended the University of Glasgow where he took the highest prize in Natural Philosophy. Shortly after his graduation, he began working in the family mercantile business J. & R. Dennistoun & Company. On November 3, 1828, he came to the United States for the firm, remaining only a short time before he returned to Scotland. In 1830, he returned to New York on Hibernia, married there, returned to Glasgow, where he stayed until 1832 when he relocated to Liverpool to manage the branch of the business there.

While in Liverpool, "in conjunction with Richard Cobden, he canvassed South Lancashire in the interests of the senior partner of Brown Brothers, the eminent banking house, about to seek the votes of that constituency for election to Parliament."In 1844, Wood returned to the United States and opened Dennistoun, Wood & Co. remaining a partner until his retirement from the firm on December 31, 1860. In 1863, he assumed the management of the British and American Bank, where he worked until 1869. In May 1869, Mayor A. Oakey Hall appointed Wood a Commissioner of Public Instruction and in May 1870, he was made a Commissioner of Docks and Ferries, serving through the administration of Mayor William F. Havemeyer until May 21, 1873. In June of 1870, he was appointed to the commission to expand Broadway to succeed Alexander Turney Stewart who retired. Wood served on the Board of Education until April 4, 1873 "when the Reform Party legislated him out of office." He was reappointed by Mayor William H. Wickham as a Commissioner of Education and became President of the Board, serving twenty years where he was instrumental in the establishment of the Normal College for the training of teachers.

Wood was a member of the Century Association and served as an elder of the Collegiate Dutch Reformed Church, although a member of the Congregational Church. In December 1828, he was elected a member of the Saint Andrew's Society of the State of New York and served as president of the society from 1865 to 1867. On September 15, 1830, he was married to daughter of John Kane and Maria Kane. Together, they were the parents of six children, including: John Walter Wood, who married Sabina Redmond, sister of Goold H. Redmond and Annie Redmond Cross. Charlotte Matilda Wood, who married the Rev. Edward Bell, Vicar of Wakefield. Elizabeth Dennistoun Wood, who married her second cousin, Thomas Leiper Kane, son of John Kintzing Kane, a United States District Court judge. Harriet Maria Wood, who died unmarried. William Wood Jr. Helen Kane Wood, who married George Burghall Watts Jr. After his first wife's death giving birth to their seventh child, he remarried to Margaret Lawrence, the daughter of James Van Horne Lawrence and Emily Augusta Lawrence.

Together, they were the parents of four children, including: Dennistoun Wood, who married Edith Phillips, daughter of Howard C. Phillips, on January 2, 1875. Chalmers Wood, who married Ellen Appleton Smith, daughter of John Cotton Smith. Henry Duncan Wood, who married Ellen E. Pulsifer, daughter of William H. Pulsifer of St. Louis, Missouri, on April 24, 1878. Van Horne Lawrence Wood, who married Bessie Dora Biggs. After the death of his second wife, he married thirdly to Helen Mason, daughter of Henry Mason and Lydia Mason, on December 6, 1883. Wood died on October 1894 at 4 West 18th Street, his home in New York City. After a funeral at the Collegiate Reformed Church, he was buried at Green-Wood Cemetery in Brooklyn. William Wood at Find a Grave Photograph of Richard James Cross. 1870, at the National Portrait Gallery, London

Dave Brubeck in Berlin

Dave Brubeck in Berlin is a 1965 live album by Dave Brubeck recorded at the Berliner Philharmonie in Berlin. The album was only released on LP in Germany, after having been recorded for radio broadcast by WDR Cologne, it was not released in the United States until 1999. The album was reviewed by Ken Dryden at Allmusic who wrote that " Desmond is witty as usual in "St. Louis Blues," though Brubeck adds an amusing Charlie Parker lick in his solo and bassist Eugene Wright shines." Dryden wrote that Brubeck's "economical solo" on "Koto Song" "...contrasts with his supposed reputation for heavy-handed playing. The group's breezy rendition of "Take the'A' Train" is followed by the inevitable "Take Five"." "St. Louis Blues" - 12:05 "Koto Song" - 7:44 "Take the "A" Train" - 8:30 "Take Five" - 6:30 Dave Brubeck - piano Paul Desmond - alto saxophone Gene Wright - double bass Joe Morello - drums Teo Macero - producer