Organolithium Reagent

An organolithium reagent is an organometallic compound with a direct bond between a carbon and a lithium atom. As the electropositive nature of lithium puts most of the charge density of the bond on the carbon atom, effectively creating a carbanion, organolithium compounds are extremely powerful bases and nucleophiles. For use as bases, butyllithiums are often used and are commercially available.

Organolithium reagents can be aggregated, with lithium coordinating to more than one carbon atom and carbon coordinating to more than one lithium atom. Three general factors affect aggregation: the electrostatic interaction between opposite charges, the coordination sphere of lithium which can be either solvent molecules or Lewis base and the steric hindrance of the hydrocarbon part.^[2] The lithium atoms tend to form triangles and higher aggregates.

In the solid state of methyllithium, 4 lithium atoms form a tetrahedron with each face capped by a methyl group which bonds simultaneously to three Li atoms (η³ hapticity). Longe-range interactions between (MeLi)₄ units are based on η³-Li-CH₃-η¹-Li bonding. Butyllithium forms a hexameric Li₆ octahedron without any long-range interactions.

Nitrocellulose

"Nitrocellulose (also: cellulose nitrate, flash paper) is a highly flammable compound formed by nitrating cellulose through exposure to nitric acid or another powerful nitrating agent. When used as a propellant or low-order explosive, it is also known as guncotton. Nitrocellulose plasticized by camphor was used by Kodak, and other suppliers, from the late 1880s as a film base in photograph, X-ray films and motion picture films; and was known as nitrate film. After numerous fires caused by unstable nitrate films, safety film started to be used from the 1930s in the case of X-ray stock and from 1948 for motion picture film."

"Henri Braconnot discovered in 1832 that nitric acid, when combined with starch or wood fibers, would produce a lightweight combustible explosive material, which he named xyloïdine. A few years later in 1838 another French chemist Théophile-Jules Pelouze (teacher of Ascanio Sobrero and Alfred Nobel) treated paper and cardboard in the same way. He obtained a similar material he called nitramidine. Both of these substances were highly unstable, and were not practical explosives."

Propyl Hexanoate

"Propyl hexanoate (C₉H₁₈O₂), also known as propyl caproate, is an ester formed by the reaction of propanol with hexanoic acid. Although it is a completely different ester, propyl hexanoate shares the same chemical formula with methyl octanoate, ethyl heptanoate, butyl pentanoate, etc. because they all have the same total carbon chain length. The scent of this ester can be described as that of blackberries, pineapple, cheese or wine."

"Due to the length of the carbon chain in this molecule, there are only minor van der Waals forces acting upon it, which is why propyl hexanoate appears as a liquid and not a solid. Dipole-dipole forces are present because of the polar covalent bonds between carbon and oxygen, while hydrogen bonding only occurs with other molecules that can hydrogen bond."

Corannulene

"Corannulene is a polycyclic aromatic hydrocarbon with chemical formula C₂₀H₁₀.^[1] The molecule consists of a cyclopentane ring fused with 5 benzene rings, so another name for it is [5]circulene. It is of scientific interest because it is a geodesic polyarene and can be considered a fragment of buckminsterfullerene. Due to this connection and also its bowl shape, corannulene is also known as a buckybowl. Corannulene exhibits a bowl-to-bowl inversion with an inversion barrier of 10.2 kcal/mol (42.7 kJ/mol) at −64 °C."

"The observed aromaticity for this compound is explained with a so-called annulene-within-an-annulene model. According to this model corannulene is made up of an aromatic 6 electron cyclopentadienyl anion surrounded by an aromatic 14 electron annulenyl cation. This model was suggested by Barth and Lawton in the first synthesis of corannulene in 1966.^[3] They also suggested the trivial name 'corannulene', which is derived from the annulene-within-an-annulene model: core + annulene."

DNA Ligase

"In molecular biology, DNA ligase is a specific type of enzyme, a ligase, (EC 6.5.1.1) that repairs single-stranded discontinuities in double stranded DNA molecules, in simple words strands that have double-strand break (a break in both complementary strands of DNA). Purified DNA ligase is used in gene cloning to join DNA molecules together. The alternative, a single-strand break, is fixed by a different type of DNA ligase using the complementary strand as a template,^[1] but still requires DNA ligase to create the final phosphodiester bond to fully repair the DNA."

"DNA ligase has applications in both DNA repair and DNA replication (see Mammalian ligases). In addition, DNA ligase has extensive use in molecular biology laboratories for Genetic recombination experiments."

"The mechanism of DNA ligase is to form two covalent phosphodiester bonds between 3' hydroxyl ends of one nucleotide, ("acceptor") with the 5' phosphate end of another ("donor"). ATP is required for the ligase reaction, which proceeds in three steps: (1) adenylation (addition of AMP) of a residue in the active center of the enzyme, pyrophosphate is released; (2) transfer of the AMP to the 5' phosphate of the so-called donor, formation of a pyrophosphate bond; (3) formation of a phosphodiester bond between the 5' phosphate of the donor and the 3' hydroxyl of the acceptor."

Anisole

"Anisole, or methoxybenzene, is the organic compound with the formula CH₃OC₆H₅. It is a colorless liquid with a smell reminiscent of anise seed, and in fact many of its derivatives are found in natural and artificial fragrances. The compound is mainly made synthetically and is a precursor to other synthetic compounds."

"Anisole undergoes electrophilic aromatic substitution reaction more quickly than does benzene, which in turn reacts more quickly than nitrobenzene. The methoxy group is an ortho/para directing group, which means that electrophilic substitution preferentially occurs at these three sites. The enhanced nucleophilicity of anisole vs benzene reflects the influence of the methoxy group, which renders the ring more electron-rich. The methoxy group strongly affects the pi cloud of the ring, more so than the inductive effect of the electronegative oxygen."

Histidine

"Histidine (abbreviated as His or H)^[2] Histidine, an essential amino acid, has a positively charged imidazole functional group. It is one of the 22 proteinogenic amino acids. Its codons are CAU and CAC. Histidine was first isolated by German physician Albrecht Kossel in 1896. Histidine is an essential amino acid in humans and other mammals. It was initially thought that it was only essential for infants, but longer-term studies established that it is also essential for adult humans."

"The imidazole sidechain of histidine has a pKa of approximately 6.0, and, overall, the amino acid has a pKa of 6.5. This means that, at physiologically relevant pH values, relatively small shifts in pH will change its average charge. Below a pH of 6, the imidazole ring is mostly protonated as described by the Henderson–Hasselbalch equation. When protonated, the imidazole ring bears two NH bonds and has a positive charge. The positive charge is equally distributed between both nitrogens and can be represented with two equally important resonance structures."

Methyl Iodide

"Methyl iodide, also called iodomethane, and commonly abbreviated "MeI", is the chemical compound with the formula CH₃I. It is a dense, colorless, volatile liquid. In terms of chemical structure, it is related to methane by replacement of one hydrogen atom by an atom of iodine. It is naturally emitted by rice plantations in small amounts.^[2] It is also produced in vast quantities estimated to be greater than 214,000 tons annually by algae and kelp in the world's temperate oceans and in lesser amounts on land due to terrestrial fungi and bacteria. Methyl iodide is used in organic synthesis as a source of methyl groups, and was approved for use as a pesticide by the United States Environmental Protection Agency in 2007.^[3] Iodomethane is a pre-plant biocide used to control insects, plant parasitic nematodes, soil borne pathogens, and weed seeds. The compound is registered for use as a preplant soil treatment for field grown strawberries, peppers, tomatoes, stone fruits, tree nuts, grape vines, ornamentals and turf and nursery grown strawberries, stone fruits, tree nuts, and conifer trees."

N-Acetyglucosamine

"N-Acetylglucosamine (N-acetyl-D-glucosamine, or GlcNAc, or NAG) is a monosaccharide derivative of glucose. It is an amide between glucosamine and acetic acid. It has a molecular formula of C₈H₁₅NO₆, a molar mass of 221.21 g/mol, and it is significant in several biological systems."

"It is part of a biopolymer in the bacterial cell wall, built from alternating units of GlcNAc and N-acetylmuramic acid (MurNAc), cross-linked with oligopeptides at the lactic acid residue of MurNAc. This layered structure is called peptidoglycan."

"GlcNAc is the monomeric unit of the polymer chitin, which forms the outer coverings of insects and crustaceans."

Sphingosine

"Sphingosine (2-amino-4-octadecene-1,3-diol) is an 18-carbon amino alcohol with an unsaturated hydrocarbon chain, which forms a primary part of sphingolipids, a class of cell membrane lipids that include sphingomyelin, an important phospholipid."

"Sphingosine can be phosphorylated in vivo via two kinases, sphingosine kinase type 1 and sphingosine kinase type 2. This leads to the formation of sphingosine-1-phosphate, a potent signaling lipid."

"Sphingolipid metabolites, such as ceramide, sphingosine and sphingosine-1-phosphate, are lipid signaling molecules involved in diverse cellular processes."