Search results
Results from the WOW.Com Content Network
The p-stands for para-, indicating that the two methyl groups in p-xylene occupy the diametrically opposite substituent positions 1 and 4. It is in the positions of the two methyl groups, their arene substitution pattern, that it differs from the other isomers, o-xylene and m-xylene. All have the same chemical formula C 6 H 4 (CH 3) 2. All ...
The prefixes ortho, meta, and para are all derived from Greek, meaning correct, following, and beside, respectively. The relationship to the current meaning is perhaps not obvious. The ortho description was historically used to designate the original compound, and an isomer was often called the meta compound.
Two chemists generally expressed the composition of a mixture in terms of numerical values relating the amount of the product to describe the equilibrium state. Cato Maximilian Guldberg and Peter Waage, building on Claude Louis Berthollet's ideas [4] [5] about reversible chemical reactions, proposed the law of mass action in 1864.
Chemical formulas can be used to describe the relative amounts of elements present in a compound. For example, the chemical formula for water is H 2 O: this means that each molecule of water is constituted by 2 atoms of hydrogen (H) and 1 atom of oxygen (O). The chemical composition of water may be interpreted as a 2:1 ratio of hydrogen atoms ...
Parylene was discovered in 1947 by Michael Szwarc as one of the thermal decomposition products of para-xylene H 3 C − C 6 H 4 − CH 3 above 1000 °C. Szwarc identified para-xylylene as the precursor by observing that reaction with iodine yielded para-xylylene di-iodide as the only product. The reaction yield was only a few percent. [1] [2]
p-DCB is produced by chlorination of benzene using ferric chloride as a catalyst: . C 6 H 6 + 2 Cl 2 → C 6 H 4 Cl 2 + 2 HCl. The chief impurity is the 1,2 isomer.The compound can be purified by fractional crystallization, taking advantage of its relatively high melting point of 53.5 °C; the isomeric dichlorobenzenes and chlorobenzene melt well below room temperature.
Chemical laws are those laws of nature relevant to chemistry. The most fundamental concept in chemistry is the law of conservation of mass , which states that there is no detectable change in the quantity of matter during an ordinary chemical reaction .
The properties of products such as their energies help determine several characteristics of a chemical reaction, such as whether the reaction is exergonic or endergonic. Additionally, the properties of a product can make it easier to extract and purify following a chemical reaction, especially if the product has a different state of matter than ...