TAILIEUCHUNG - ORGANIC CHEMISTRY: REACTION MECHANISMS

Although processes for the production of LVOC are extremely diverse and complex, they are typically composed of a combination of simpler activities and equipment that are based on similar scientific and engineering principles. Chapter 2 describes how unit processes, unit operations, site infrastructure, energy control and management systems are combined and modified to create a production sequence for the desired LVOC product. Most LVOC processes can be described in terms of five distinct steps, namely: raw material supply / work-up, synthesis, product separation / refining, product handling / storage, and emission abatement | MODULE 6 ORGANIC CHEMISTRY REACTION MECHANISMS Acids and Bases Carbanion Attack at a Carbonyl Group The Mechanism of Reduction Reactions Nucleophilic Attack by Water Nucleophilic Attack by an Alcohol Addition Elimination Reactions of Carboxylic Acid Derivatives Free Radical Reactions Bimolecular Nucleophilic Substitution or SN2 Reactions Unimolecular Nucleophilic Substitution or SN1 Reactions Elimination Reactions Substitution versus Elimination Reactions ACIDS AND BASES As noted in Section for more than 300 years chemists have classified substances that behave like vinegar as acids while those that have properties like the ash from a wood fire have been called alkalies or bases. Today when chemists use the words acid or base they refer to a model developed independently by Br0nsted Lowry and Bjerrum. Since the most explicit statement of this theory was contained in the writings of Br0nsted it is most commonly known as the Br0nsted acid-base theory. Br0nsted Acid-Base Theory Br0nsted argued that all acid-base reactions involve the transfer of an H ion or proton. Water reacts with itself for example by transferring an H ion from one molecule to another to form an H3O ion and an OH ion. H2O H2O -- H3O OH I_I r t -H 1 2 ORGANIC REACTION MECHANISMS According to the theory a Bronsted acid is a proton donor and a Bronsted base is a proton acceptor. Acids are often divided into categories such as strong and weak. One measure of the strength of an acid is the acid dissociation equilibrium constant Ka for that acid. K HO - A I Ka HA When Ka is relatively large we have a strong acid. HCl Ka 1 X 106 When it is small we have a weak acid. CH3CO2H Ka X 10 5 When it is very small we have a very weak acid. H2O Ka X 10 16 In 1909 S. P. L. S0renson suggested that the enormous range of concentrations of the H3O and OH ions in aqueous solutions could be compressed into a more manageable set of data

• Hoá dầu
• Technological changes
• Infrastructure development
• Inventory of resources
• Endowment opportunities
• Threats to atmospheric resources
• realizing opportunities
• ATMA Agriculture technological
• Management agency
• Changes in knowledge
• Changes in skill and changes
• Adoption of farm
• natural resources
• alternative measures
• substitution possibilities
• resource scarcity
• Important caveats