【2018年必威体育精装版整理】chapterVI.ppt

6.7 Describing a Reaction: Equilibria, Rates, and Energy Changes The ratio of products to reactants is dependent on their relative “energy content”. Mathematically, For a reaction: for example, Enthalpy（焓） change energy of: bonds broken - bonds formed (-ve: exothermic, +ve: endothermic) Entropy（熵）change: molecular disorder 混乱度 of: products - reactants Gibbs free-energy change equilibrium constant gas constant temperature G（自由能） is the energy difference between reactants 反应物 and products 产物 (-ve: exergonic 放热 , +ve: endergonic 吸热 ). NOTE: equilibrium position of a reaction ≠ rate of a reaction Explanation of Thermodynamic Quantities: DG°=DH°―TDS° Rate ? Is the reaction fast or slow? Equilibrium ? In what direction does the reaction proceed? * Chapte 6. An Overview of Organic Reactions ? proper use of curved arrows to illustrate mechanisms ? qualitative understanding of ?G ? the use of energy diagrams to describe reactions Key focus: 6.1 Kinds of Organic Reactions 有机反应类型 Common patterns describe the changes in organic reactions. 2 reactants add together to form a single new product. Addition reactions 加成反应: Ethylene (an alkene) Bromoethane (an alkyl halide) A + B C 2 reactants exchange parts to give 2 new products. Elimination reactions 消去反应: A single reactant split into 2 products. Substitution reactions 取代反应: Methyl acetate (an ester) Acetic acid (a carboxylic acid) Methanol (an alcohol) Ethanol (an alcohol) Ethylene (an alkene) A B + C A single reactant undergoes a reorganization of bonds to yield an isomeric product. Rearrangement reactions 重排反应: Dihydroxyacetone phosphate Glyceraldehyde 3-phosphate Kinds of Organic Reactions 有机反应类型 6.2 How Organic Reactions Occur:  Reaction Mechanisms ? Reactions occur in defined steps that lead from reactant to product. ? The mechanism describes the steps behind the observed changes in a reaction. ? We classify the types of steps in a sequence. ? A step involves eith