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Rosefuran
Rosefuran (3-methyl-2-prenylfuran) is a liquid boiling at 103-104 °C (at 50 mm Hg), with a density of 0.9089 g/cm3 (at 30 °C), less than that of water. It is an aroma chemical which is a minor constituent of the aroma of the rose (Rosa damascene). Rosefuran is a 2,3-disubstituted furan (3-methyl-2-(3-methyl-2-buten-1-yl)furan). It has an odor threshold of 200 ppb and constitutes 0.16% of Bulgarian rose oil. Rosefuran has been established as a female sex pheromone of an acarid mite, Caloglyphus sp. Concentrations of less than 100 ng of synthetic rosefuran caused sexual excitation in males of the species. Synthesis Rosefuran was synthesized in 1968 by George Büchi via the organomercury compound bis(3-methyl-2-furyl)mercury. Rosefuran has been synthesized in many steps from common starting materials starting with prenyl chloride (3-methyl-but-2-en-1-yl chloride). Rosefuran has also been synthesized via cyclization of suitable acyclic precursors, such as, 5-ox ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
George Büchi
George Hermann Büchi (August 1, 1921 – August 28, 1998) was a Swiss organic chemist and professor at the Massachusetts Institute of Technology. "Paternò's reaction", known since the early twentieth century, was renamed to the "Paternò–Büchi reaction The Paternò–Büchi reaction, named after Emanuele Paternò and George Büchi, who established its basic utility and form, is a photochemical reaction, specifically a 2+2 photocycloaddition, which forms four-membered oxetane rings from an excit ..." based on enhancements made to it by Büchi's research group. Büchi died at the age of 77 of heart failure while hiking with his wife in Switzerland. References 1921 births 1998 deaths Organic chemists Massachusetts Institute of Technology faculty Members of the United States National Academy of Sciences Swiss expatriates in the United States {{chemist-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wittig Reaction
The Wittig reaction or Wittig olefination is a chemical reaction of an aldehyde or ketone with a triphenyl phosphonium ylide called a Wittig reagent. Wittig reactions are most commonly used to convert aldehydes and ketones to alkenes. Most often, the Wittig reaction is used to introduce a methylene group using methylenetriphenylphosphorane (Ph3P=CH2). Using this reagent, even a sterically hindered ketone such as camphor can be converted to its methylene derivative. Stereochemistry For the reaction with aldehydes, the double bond geometry is readily predicted based on the nature of the ylide. With unstabilised ylides (R3 = alkyl) this results in (''Z'')-alkene product with moderate to high selectivity. With stabilized ylides (R3 = ester or ketone), the (''E'')-alkene is formed with high selectivity. The (''E'')/(''Z'') selectivity is often poor with semistabilized ylides (R3 = aryl). To obtain the (''E'')-alkene for unstabilized ylides, the Schlosser modification of t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Claisen Rearrangement
The Claisen rearrangement is a powerful carbon–carbon bond-forming chemical reaction discovered by Rainer Ludwig Claisen. The heating of an allyl vinyl ether will initiate a ,3sigmatropic rearrangement to give a γ,δ-unsaturated carbonyl, driven by exergonically favored carbonyl CO bond formation (ΔΔHf = -327kcalmol−1). Mechanism The Claisen rearrangement is an exothermic, concerted (bond cleavage and recombination) pericyclic reaction. Woodward–Hoffmann rules show a suprafacial, stereospecific reaction pathway. The kinetics are of the first order and the whole transformation proceeds through a highly ordered cyclic transition state and is intramolecular. Crossover experiments eliminate the possibility of the rearrangement occurring via an intermolecular reaction mechanism and are consistent with an intramolecular process. There are substantial solvent effects observed in the Claisen rearrangement, where polar solvents tend to accelerate the reaction to a great ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lithium Diisopropylamide
Lithium diisopropylamide (commonly abbreviated LDA) is a chemical compound with the molecular formula . It is used as a strong base and has been widely utilized due to its good solubility in non-polar organic solvents and non-nucleophilic nature. It is a colorless solid, but is usually generated and observed only in solution. It was first prepared by Hamell and Levine in 1950 along with several other hindered lithium diorganylamides to effect the deprotonation of esters at the α position without attack of the carbonyl group. Preparation and structure LDA is commonly formed by treating a cooled (0 to −78 °C) mixture of tetrahydrofuran and diisopropylamine with ''n''-butyllithium. When dissociated, the diisopropylamide anion can become protonated to form diisopropylamine. Diisopropylamine has a p''K''a value of 36. Therefore, its conjugate base is suitable for the deprotonation of compounds with greater acidity, importantly, such weakly acidic compounds (carbon acids) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
N-butyllithium
''n''-Butyllithium C4H9Li (abbreviated ''n''-BuLi) is an organolithium reagent. It is widely used as a polymerization initiator in the production of elastomers such as polybutadiene or styrene-butadiene-styrene (SBS). Also, it is broadly employed as a strong base (superbase) in the synthesis of organic compounds as in the pharmaceutical industry. Butyllithium is commercially available as solutions (15%, 25%, 1.5 M, 2 M, 2.5 M, 10 M, etc.) in alkanes such as pentane, hexanes, and heptanes. Solutions in diethyl ether and THF can be prepared, but are not stable enough for storage. Annual worldwide production and consumption of butyllithium and other organolithium compounds is estimated at 2000 to 3000 tonnes. Although butyllithium is colorless, ''n''-butyllithium is usually encountered as a pale yellow solution in alkanes. Such solutions are stable indefinitely if properly stored,. but in practice, they degrade upon aging. Fine white precipitate (li ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crotonaldehyde
Crotonaldehyde is a chemical compound with the formula CH3CH=CHCHO. The compound is usually sold as a mixture of the ''E''- and ''Z''-isomers, which differ with respect to the relative position of the methyl and formyl groups. The ''E''-isomer is more common (data given in Table is for the ''E''-isomer). This lachrymatory liquid is moderately soluble in water and miscible in organic solvents. As an unsaturated aldehyde, crotonaldehyde is a versatile intermediate in organic synthesis. It occurs in a variety of foodstuffs, e.g. soybean oils. Production and reactivity Crotonaldehyde is produced by the aldol condensation of acetaldehyde: :2 CH3CHO → CH3CH=CHCHO + H2O Crotonaldehyde is a multifunctional molecule that exhibits diverse reactivity. It is a prochiral dienophile. It is a Michael acceptor. Addition of methylmagnesium chloride produces 3-penten-2-ol. Polyurethane catalyst ''N'',''N'',''N''′,''N''′-tetramethyl-1,4-butanediamine (also known as NIAX TMBD ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Grignard Reaction
The Grignard reaction () is an organometallic chemical reaction in which alkyl, allyl, vinyl, or aryl-magnesium halides (Grignard reagent) is added to a carbonyl group in an aldehyde or ketone. This reaction is important for the formation of carbon–carbon bonds. The reaction of an organic halide with magnesium is ''not'' a Grignard reaction, but provides a Grignard reagent. : Grignard reactions and reagents were discovered by and are named after the French chemist François Auguste Victor Grignard ( University of Nancy, France), who published it in 1900 and was awarded the 1912 Nobel Prize in Chemistry for this work. Reaction mechanism Because carbon is more electronegative than magnesium, the carbon attached to magnesium functions as a nucleophile and attacks the electrophilic carbon atom that is present within the polar bond of a carbonyl group. The addition of the Grignard reagent to the carbonyl typically proceeds through a six-membered ring transition state. Based ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Perilla
''Perilla'' is a genus consisting of one major Asiatic crop species ''Perilla frutescens'' and a few wild species in nature belonging to the mint family, Lamiaceae. The genus encompasses several distinct varieties of Asian herb, seed, and vegetable crop, including '' P. frutescens'' (deulkkae) and ''P. frutescens'' var. ''crispa'' (shiso). The genus name ''Perilla'' is also a frequently employed common name ("perilla"), applicable to all varieties. Perilla varieties are cross-fertile and intra-specific hybridization occurs naturally. Some varieties are considered invasive. Taxa and synonyms The classification of ''Perilla'' is confused, partly because botanists struggled with distinguishing the two distinct cultigens as different species or variations. Until a few decades ago, ''P. frutescens'' var. ''crispa'' was regarded as a species in its own right, distinct from ''P. frutescens'', although it was well established that these types readily cross-pollinate. An early exa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bangladesh
Bangladesh (}, ), officially the People's Republic of Bangladesh, is a country in South Asia. It is the eighth-most populous country in the world, with a population exceeding 165 million people in an area of . Bangladesh is among the most densely populated countries in the world, and shares land borders with India to the west, north, and east, and Myanmar to the southeast; to the south it has a coastline along the Bay of Bengal. It is narrowly separated from Bhutan and Nepal by the Siliguri Corridor; and from China by the Indian state of Sikkim in the north. Dhaka, the capital and largest city, is the nation's political, financial and cultural centre. Chittagong, the second-largest city, is the busiest port on the Bay of Bengal. The official language is Bengali, one of the easternmost branches of the Indo-European language family. Bangladesh forms the sovereign part of the historic and ethnolinguistic region of Bengal, which was divided during the Partition of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
