An aldehyde is a compound containing a functional group with the structure −CHO, consisting of a carbonyl center with the carbon atom bonded to hydrogen and to an R group, any generic alkyl or side chain. The group—without R—is the aldehyde group known as the formyl group. Aldehydes are common in organic chemistry, many fragrances are or contain aldehydes. Aldehydes feature an sp2-hybridized, planar carbon center, connected by a double bond to oxygen and a single bond to hydrogen; the C–H bond is not ordinarily acidic. Because of resonance stabilization of the conjugate base, an α-hydrogen in an aldehyde is far more acidic, with a pKa near 17, compared to the acidity of a typical alkane; this acidification is attributed to the electron-withdrawing quality of the formyl center and the fact that the conjugate base, an enolate anion, delocalizes its negative charge. Related to, the aldehyde group is somewhat polar; the formyl proton itself does not undergo deprotonation. The anionic species formally derived from deprotonation of an aldehyde proton, known as an acyl anion, is unstable and must be kept at low temperatures.
In fact, with the exception of certain hindered dialkylformamides, the synthesis of acyl anions by direct deprotonation is not a feasible route, since the deprotonated species will immediately add to the reactive carbonyl of the starting material to form an acyloin compound. For this reason, the acidity of the formyl proton is difficult to measure. In the case of HCONiPr2, the acidity of the formyl group was found to be close to that of diisopropylamine; the gas-phase acidity of formaldehyde was found to be 1,640 kJ/mol, making it more acidic than hydrogen and ammonia, but less acidic than water in the gas phase. Aldehydes can exist in either the enol tautomer. Keto–enol tautomerism is catalyzed by either acid or base; the enol is the minority tautomer, but it is more reactive. At around 360 kJ/mol, the formyl C–H bond is weaker than that of a typical bond between hydrogen and an sp2-hybridized carbon, thus aldehydes are prone to undergo hydrogen-atom abstraction in the presence of free radicals, a fact accounts for the ease with which aldehydes undergo autoxidation.
The common names for aldehydes do not follow official guidelines, such as those recommended by IUPAC, but these rules are useful. IUPAC prescribes the following nomenclature for aldehydes: Acyclic aliphatic aldehydes are named as derivatives of the longest carbon chain containing the aldehyde group. Thus, HCHO is named as a derivative of methane, CH3CH2CH2CHO is named as a derivative of butane; the name is formed by changing the suffix -e of the parent alkane to -al, so that HCHO is named methanal, CH3CH2CH2CHO is named butanal. In other cases, such as when a -CHO group is attached to a ring, the suffix -carbaldehyde may be used. Thus, C6H11CHO is known as cyclohexanecarbaldehyde. If the presence of another functional group demands the use of a suffix, the aldehyde group is named with the prefix formyl-; this prefix is preferred to methanoyl-. If the compound is a natural product or a carboxylic acid, the prefix oxo- may be used to indicate which carbon atom is part of the aldehyde group. If replacing the aldehyde group with a carboxyl group would yield a carboxylic acid with a trivial name, the aldehyde may be named by replacing the suffix -ic acid or -oic acid in this trivial name by -aldehyde.
The word aldehyde was coined by Justus von Liebig as a contraction of the Latin alcohol dehydrogenatus. In the past, aldehydes were sometimes named after the corresponding alcohols, for example, vinous aldehyde for acetaldehyde; the term formyl group is derived from the Latin word formica "ant". This word can be recognized in the simplest aldehyde, in the simplest carboxylic acid, formic acid. Aldehydes have properties that are diverse and that depend on the remainder of the molecule. Smaller aldehydes are more soluble in water and acetaldehyde so; the volatile aldehydes have pungent odors. Aldehydes arylaldehydes, degrade in air via the process of autoxidation; the acyl hydroperoxide is generated, which comproportionates with the starting material to generate two equivalents of the carboxylic acid. Old bottles of benzaldehyde, a liquid, will accumulate a crusty solid on the bottle cap or suspended in the bulk liquid; this material is benzoic acid. The two aldehydes of greatest importance in industry and acetaldehyde, have complicated behavior because of their tendency to oligomerize or polymerize.
Formaldehyde in particular is sold as the polymer paraformaldehyde as well as the trimer 1,3,5-trioxane. In addition to the inconveniently low-boiling monomer, acetaldehyde is available as the trimer paraldehyde and tetramer metaldehyde. In general, higher aliphatic aldehydes will accumulate a substantial amount of oligomer upon long-term storage and must be freshly distilled when a reaction calls for the monomeric starting material, they tend to hy
Tucking Mill is a small hamlet within the parish of Monkton Combe, England. It was a key point on the now disused Somerset Coal Canal, it is at the southern end of the Two Tunnels Greenway which follows the disused railway trackbed of the Somerset and Dorset Joint Railway from East Twerton through the Bath suburb of Oldfield Park to the Devonshire Tunnel, emerging into Lyncombe Vale before entering the Combe Down Tunnel, coming out to cross Tucking Mill Viaduct into Midford. There is a small reservoir, now a fishery for the disabled. From 1798 until 1810 Tucking Mill was the home of William Smith, an English geologist, credited with creating the first nationwide geological map, he is known as the "Father of English Geology" for collating the geological history of England and Wales into a single record. He worked on the Somerset Coal Canal. There is a plaque on Tucking Mill Cottage saying that it was Smith's home, erected in 1888, on the mill, demolished in 1927, the tablet was mislaid; when the plaque was rediscovered in the 1930s the Geological Society of London and the Bath Royal Literary and Scientific Institution placed it on the 18th century cottage.
However, it is now believed that he lived in the nearby Tucking Mill House. During his occupation he built a small railway to transport stone from a quarry at Kingham Field, Combe Down to the canal. From 1883 until the end of World War II it was the site of a fuller's earth factory. George Dames and his brother Charles Richard Dames set up a mine in Horsecombe Vale. At the bottom of the valley was the pan grinding works where water from Horsecombe Brook was used to make a slurry from which sand settled at the bottom of troughs; the slurry passed through an earthenware pipe to Tucking Mill, where a second stage of sedimentation took place in large troughs where it settled for up to 30 days. Once the water had been drained by sluices the damp caked earth was carried in wooden trams to kilns where it was dried for three to four days; the product was used in pharmaceutical industries. The original uses in woollen production no longer used fuller's earth. A railway siding at Midford railway station was built to load fuller's earth
Worldbeat is a music genre that blends pop music or rock music with world music or traditional music. Worldbeat is similar to other cross pollination labels of contemporary and roots genres, which suggest a rhythmic, harmonic or textural contrast between its modern and ethnic elements. Worldbeat is akin to world fusion and global fusion, each of which manifest as a blend of ethnic music tradition and Western, popular music; these particular music genres can reflect in a cross-blend of more than one "traditional" flavor, producing innovative, hybrid expressions of world music. As with most "world"-laden genre categories, worldbeat is not defined as are the many classic world music subgenres, such as gamelan, or calypso. In general, the expanding family of ethnic music subgenres under the world music umbrella represents an intrinsically nebulous terminology, which depending on how one interprets a particular hybrid of world music, can be interchangeable to a significant degree. Worldbeat defines a hybrid of what can be listed under the generalized world music term though it features a prominent interbreeding with elements of Western, pop music.
As an ethnically coloured genre, worldbeat is a part of the world music movement, influencing popular music in every corner of the globe. This is due to the advance of digital music production and the availability of high quality ethnic music samples to artists and producers in the recording arts; the globalization of texture and style between indigenous and modern music genres has expanded the scope of 21st century, popular music, continues to reshape how the world defines the increasing number of genres conceived with world music elements. Worldbeat, world fusion and global fusion are hybrid-genres that have evolved under the world music genre, their most prominent feature is an obvious meld between pop and indigenous culture, which causes them to be indistinguishable from one another. Contemporary genre hybrids with world music elements proliferate in proportion to the globalization of music culture. In music catalogs, hybrid genres are only given the database choice of "world", thus the perception of what can define world music has evolved to include pop influences.
There is disagreement whether all pop and traditional music hybrids exhibiting prominent ethno-influences, such as worldbeat, belong under the world music umbrella. Music genre terms that contain "world" are subject to a ambiguous consumer definition, due to the confusing similarity and overlapping interpretation of these categories; the world music category is inherently diverse, offers limitless possibility for application in hybrid form in mainstream, market-driven music. Worldbeat as a small subgenre of popular music has a mounting consumer-perception as a hybrid subgenre of world music, to the chagrin of world music purists. In its context as a liberally termed subgenre under the world music umbrella, worldbeat is similar to world fusion and global fusion; the distinctions that delineate these hybrid, "world" terms are slight, in many ways they are still being defined. Worldbeat as a coined genre emerged in the mid-1980s when popular, mainstream artists like David Byrne and Paul Simon began incorporating world music influences into their sound.
The most prominent influences came from Africa, South America the Middle East and Latin America, though now encompass an ever-widening range of ethnic diversity. It has remained a thriving subgenre of popular and world music, while continuing to influence new artists those appearing on today's growing roster of indie record labels; some of worldbeat's most integrated folk elements include bossa nova, Afrobeat, qawwali, rai, samba and tango. Ambient music New Age music Folk music Worldbeat Music Albums on AllMusic