【正文】 with respect to the other so that there is no overlap between 2p orbitals on adjacent carbonsCis,Trans Isomerism in AlkenesCis,trans isomers: isomers that have the same connectivity but a different arrangement of their atoms in space due to the presence of either a ring or a carboncarbon double bondIUPAC Nomenclature1. Number the longest chain of carbon atoms that contains the double bond in the direction that gives the carbons of the double bond the lowest numbers2. Locate the double bond by the number of its first carbon3. Name substituents4. Number the carbon, locate and name substituents, locate the double bond, and name the main chainCommon NamesDespite the precision and universal acceptance of IUPAC nomenclature, some alkenes, particularly lowmolecularweight ones, are known almost exclusively by their mon namesThe Cis,Trans SystemIf one of the sp2 carbons of the double bond is attached to two identical substituents, there is only one possible structure for the alkene. In other words, cis and trans isomers are not possible for an alkene that has identical substituents attached to one of the doublebonded carbons.uses priority rules if groups of higher priority are on the same side, the configuration is Z (German, zusammen)if groups of higher priority are on opposite sides, the configuration is E (German, entgegenthe two isomers are different pounds with different physical properties, such as different boiling points and different dipole moments.The relative priorities of the two groups bonded to an carbon are determined using the following rules:Rule 1. The relative priorities of the two groups depend on the atomic numbers of the atoms that are bonded directly to the carbon. The greater the atomic number, the higher is the priority.Rule 2. If the two substituents bonded to an sp2 carbon start with the same atom (there is a tie), you must move outward from the point of attachment and consider the atomic numbers of the atoms that are attached to the “tied” atoms.Rule 3. If an atom is doubly bonded to another atom, the priority system treats it as if it were singly bonded to two of those atoms. If an atom is triply bonded to another atom, the priority system treats it as if it were singly bonded to three of those atoms.Rule 4. In the case of isotopes (atoms with the same atomic number, but different mass numbers), the mass number is used to determine the relative priorities. Reaction Mechanism electrophile : An electrondeficient atom or molecule is called an electrophile. nucleophile : An electronrich atom or molecule is called a nucleophile. Reaction MechanismsA reaction mechanism describes how a reaction occurswhich bonds are broken and which new ones are formedthe order and relative rates of the various bondbreaking and bondforming stepsif in solution, the role of the solventif there is a catalyst, the role of a catalystthe position of all atoms and energy of the entire system during the reactionGibbs free energy change, ΔG0: a thermodynamic function relating enthalpy, entropy, and temperatureexergonic reaction: a reaction in which the Gibbs free energy of the products is lower than that of the reactants。) C: a carbon bonded to four other carbonsNomenclature IUPACParent name: the longest carbon chainSubstituent: a group bonded to the parent chain alkyl group: a substituent derived by removal of a hydrogen from an alkane。 carbonSecondary (2176。 these electrons are used to form chemical bonds and in chemical reactionsLewis dot structure: the symbol of an element represents the nucleus and all inner shell electronsdots represent valence electronsLewis Dot Structures for Elements 118 Lewis Model of BondingAtoms bond together so that each atom acquires an electron configuration the same as that of the noble gas nearest it in atomic numberan atom that gains electrons bees an anionan atom that loses electrons bees a cationthe attraction of anions and cations leads to the formation of ionic solidsan atom may share electrons with one or more atoms to plete its valence shell。ns Jakob Berzelius gave names to the two kinds of materials. Compounds derived from living organisms were believed to contain an unmeasurable vital force—the essence of life. These he called ‘inorganic’. Compounds derived from mineralsthose lacking that vital forcewere “inorganic”.(3) In 1816, Michel Chevreul found that soap, prepared by the reaction of alkali with animal fat, could be separated into several pure organic pounds, which he termed fatty acid. For the first time, one organic substance (fat) was converted into others (fatty acids plus glycerin) without the intervention of an outside vital force.（4）In 1828 when Friedrich W246。the unhybridized 2p orbitals are perpendicular to each other and to the line created by the axes of the two sp hybrid orbitalsBonding in Acetylene, C2H2Hybrid OrbitalsChapter 2 Alkane and cycloalkane Alkane The definition of alkaneAlkanes are posed of only carbon atoms and hydrogen atoms and contain only single bonds. Compounds that contain only carbon and hydrogen are called hydrocarbons, so an alkane is a hydrocarbon that has only single bonds. Alkanes in which the carbons form a continuous chain with no branches are called straightchain alkanes. The names of several straightchain alkanes are given in Table . It is important that you learn the names of at least the first 10.The family of alkanes shown in the table is an example of a homologous series. A homologous series (homos is Greek for “the same as”) is a family of pounds in which each member differs from the next by one methylene (CH2) group. The members of a homolo