Chapter 7: Chemical Reactions, Bond Energy, and Kinetics- A chem rxn involves making new chem bonds and breaking old chem bond- Each bond has inherent E which is released when the bond is brokeno Likewise, it will cost that amount of E to make the bond- Hydrolysis: an acid-base rxn b/w the alkoxide base and the H3O+ as the acid- All rxns involve modification of the original molecule (starting molecule) and formation of anew molecule (the product) w/ the gain of 1+ atoms or groups, loss of 1+ atoms or groups, ortransformation of 1 functional group into another- Alipathic Nucleophile Substitution Reaction: when one group or atom replace another, the first group substitutes for the 2nd - Nucleophile Acyl Substitution: when a nucleophile attacks a carbonyl—the acyl C—the pi bond is broken and a new covalent bond is formed b/w the nucleophile and the acyl C- Addition Reaction: the sp2 C’s are transformed to sp3 C’so An acid-base rxn- Elimination Reaction: sp3 C’s are transformed into sp2 C’s in a new pi bond- Carbon-Carbon Bond-Forming Reaction: a C—C bond is formed- Functional Group Transformation or Functional Group Interchange Reaction: if no C—C bond is formed, but the functional group is simply changed or modified- The E released when a sigma bond is cleaved (bond breaking) is called bond dissociation E o The amount of E released when the bond is broken and the amount required to make the bondo The exact E of a bond depends on the bond length (function of the size of the atoms),electronegativity considerations, solvent in some case, and other bonds that are connected to the atom of interesto One parameter used to predict whether or not a chem rxn is likely to proceed to give a particular producto Change in E during a rxn: ΔH – means that E is released exothermic (exergonic)- Said to be spontaneous (if ΔG is -) b/c it produces enough E duringthe course of the rxn to be self-sustaining- Releases E in the form of work from the system to the surroundings + means E is put in endothermic (endergonic)- Usually not spontaneous b/c less E is produced during the rxn than is required to keep it going- Absorbs E in the form of work from the surroundings into the systemo A spontaneous rxn should continue to produce a product once it has started.o A nonspontaneous rxn requires more E than is supplied by breaking and making bonds in order to continue, and will likely require more vigorous rxn conditions- Transition State: the point in the rxn where the starting materials begin to react and begin thetransition to the producto There’s no formal bond yet, but the bonding process as begun and is represented by adashed line [A-------B]o Midpoint of the rxn and is an E associated w/ making and breaking bonds as the rxn proceeds- Synchronous: a rxn w/ only one step to get to the final product- Intermediates: transient products that are formed in a rxn prior to the formation of the final producto Brackets indicate a transient species to set it apart from the rest of the rxno A rxn that’s not isolated, but reacts to give another more stable producto W/ an intermediate, there are 2 rxnso Can be a carbocation, carboanion, or a radical- Mechanism: a rxn sequence that includes each reactive intermediate produced on the way to the final product- Cations: electron-deficient species that bear a + charge and quickly react w/ species that can donate electronso Carbocations or carbenium ions: have a + charge on a C atom FC of C= +1 Formed when a covalent bond to C is broken s such a way that 2 electrons are transferred to one atom and the C receives no electrons during the transfer- Called a heterolytic cleavage: breaking a bond in such a manner that both electrons are transferred to one atom and no electrons to the other  The C of a carbocation is sp2 hybridized and must have trigonal planar geometry Will react w/ another species that can donate the 2 missing electrons to giveit 8, satisfy the valence requirements of C, and form the 4th bond to make C tetravalent  High-E intermediates, and relatively high activation E’s are required for their formation Once formed, carbocations have a low activation E for rxn w/ the nucleophile An “empty” p-orbital that’s localized on an atom, in this case C- Anions: electron-rich species that easily donates electrons to an electron-defiecient specieso Carboanion: a – charge resides on the C  FC of C= -1 When a carboanion reacts w/ another C atom, it’s classified as a nucleophile Formed by breaking a covalent bond in such a way that 2 electrons are transferred to the C involved in the bond, and the 2nd atoms receives no electrons during the transfer (a heterolytic cleavage) The pair of electrons reside in a p-orbital A “filled” p-orbital that’s localized on an atom, in this case C- Radicals: a species w/ one unshared electron in a p-orbital, which makes it very reactive, and it will react to form a bond in a manner diff of that of a cation or an anion o Only has 1 electron and it will react w/ another radical to form a covalent bond, where each species donates 1 electrono Also react w/ neutral species to form a new s-covalent bond and a new radicalo 3 covalent bonds and 1 unpaired electrono A high- E species and a very reactive intermediateo The single electron in the orbital will slightly repel the electrons in the covalent bonds, so one expect a squashed tetrahedron, however, there’s evidence that a planar structure is probably the lowest-E structure o One way to form a C radical is by chem rxn b/w a neutral species and a preformed radicalo Can be formed by breaking a covalent bond in a way that one electron is transferred to each of the 2 atoms involved in that bond Homolytic Cleavage- Chem rxns are driven by changes in Eo Heating imparts E to the molecules in a rxn, which will increase the E of the systemo Molecules absorb E from their environment by collision w/ side of rxn vessel (flask) or w/ another atom or molecule This E is utilized in making and breaking bonds ΔG is the E of the entire system (free E)- Whether or not a chem rxn will proceed spontaneously is determined by ΔGo If the # of particles for a rxn remains the same or decreases, the magnitude of the entropy is small.o If the # of particles greatly increases during the course of a rxn, then entropy increaseso If entropy is assumed to be 0, the ΔG= ΔH However, ignoring the entropy term is an