Learning Chemistry

Aniline  is an  organic compound  with the  formula  C 6 H 5 NH 2 . Consisting of a  phenyl group attached to an  amino group , aniline is the prototypical aromatic amine. Its main use is in the manufacture of precursors to  polyurethane  and other industrial chemicals. Like most volatile amines, it possesses the odour of rotten fish. It ignites readily, burning with a smoky flame characteristic of aromatic compounds. Aniline is a planar molecule. The amine is nearly planar owing to conjugation of the lone pair with the aryl substituent. The C-N distance is correspondingly shorter. In aniline, the C-N and C-C distances are close to 1.39 Å, indicating the  π -bonding between N and C. Industrial aniline production involves two steps. First,  benzene  is  nitrated  with a concentrated mixture of  nitric acid  and  sulfuric acid  at 50 to 60 °C to yield  nitrobenzene . The nitrobenzene is then  hydrogenated  (typically at 200–300 °C) in the presence of metal  catalysts . The reduction

Methyl orange is a pH indicator frequently used in titrations because of its clear and distinct colour change. Because it changes colour at the pH of a midstrength acid, it is usually used in titrations for acids. Unlike a universal indicator, methyl orange does not have a full spectrum of colour change, but has a sharper end point. Methyl orange shows red colour in acidic medium and yellow colour in basic medium. In a solution becoming less acidic, methyl orange moves from red to orange and finally to yellow with the reverse occurring for a solution increasing in acidity.The entire color change occurs in acidic conditions.In an acid, it is reddish and in alkali, it is yellow. Methyl orange has a pKa of 3.47 in water at 25 °C (77 °F). Modified (or screened) methyl orange, an indicator consisting of a solution of methyl orange and xylene cyanol, changes from grey-violet to green as the solution becomes more basic. Since acidic solutions have low pH values, it will be red and tr

Malachite green is an organic compound that is used as a dyestuff and controversially as an antimicrobial in aquaculture. Malachite green is traditionally used as a dye for materials such as silk, leather, and paper. Despite its name the dye is not prepared from the mineral malachite, and the name just comes from the similarity of color. Malachite green is classified in the dyestuff industry as a triarylmethane dye and also using in pigment industry. Formally, malachite green refers to the chloride salt [C6H5C(C6H4N(CH3)2)2]Cl, although the term malachite green is used loosely and often just refers to the colored cation. The oxalate salt is also marketed. The anions have no effect on the color. The intense green color of the cation results from a strong absorption band at 621 nm (extinction coefficient of 105 M−1 cm−1). Malachite green is prepared by the condensation of benzaldehyde and dimethylaniline to give leuco malachite green (LMG): C6H5CHO + 2 C6H5N(CH3)2 → C6H5CH(C6H4N

Phenol formaldehyde resins (PF) or phenolic resins are synthetic polymers obtained by the reaction of phenol or substituted phenol with formaldehyde. Used as the basis for Bakelite, PFs were the first commercial synthetic resins (plastics). They have been widely used for the production of molded products including billiard balls, laboratory countertops, and as coatings and adhesives. They were at one time the primary material used for the production of circuit boards but have been largely replaced with epoxy resins and fiberglass cloth, as with fire-resistant FR-4 circuit board materials. There are two main production methods. One reacts phenol and formaldehyde directly to produce a thermosetting network polymer, while the other restricts the formaldehyde to produce a prepolymer known as novolac which can be moulded and then cured with the addition of more formaldehyde and heat. There are many variations in both production and input materials that are used to produce a wide variety

Urea-formaldehyde , also known as   urea-methanal, so named for its common synthesis pathway and overall structure,is a   non-transparent   thermosetting   resin   or   polymer. It is produced from   urea   and   formaldehyde. These resins are used in   adhesives, finishes,   particle board,   MDF, and molded objects. It was first synthesized in 1884 by Hölzer, who was working with Bernhard Tollens. In 1919, Hanns John (1891–1942) of Prague, Czechoslovakia obtained the first patent for urea-formaldehyde resin. UF and related amino resins are a class of   thermosetting resins   of which urea-formaldehyde resins make up 80% produced globally. Examples of amino resins use include in automobile tires to improve the bonding of rubber to tire cord, in paper for improving tear strength, in molding electrical devices, jar caps, etc Urea-formaldehyde resin's attributes include high tensile strength, flexural modulus, and a high heat distortion temperature, low water absorption,