【正文】 n nature, including synthetic fabrics, plastics, synthetic rubber, medicines, and even things like photographic film and Super glue. Many of these synthetic pounds prevent shortages of naturally occurring products. How to study Organic ChemistryOrganic chemistry is a study of the relationship between the structure of molecules and their reaction.If you expect to learn organic chemistry well, you must draw and redraw the structures of pounds and write out equations as you are studying.To study effectively, you should read the assignments before attending lectures. Spend most of you study time working out the problems. Work all of the problems, no matter how simple they seem, in writing and in full detail.In addition, the study guide contains concept maps, which are summaries of important ideas presented in outline form. Covalent Bonding amp。 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。 these bonds are called polar covalent bonds Formation of IonsA rough guideline: ions will form if the difference in electronegativity between interacting atoms is or greaterexample: sodium (EN ) and fluorine (EN )we use a singleheaded (barbed) curved arrow to show the transfer of one electron from Na to Fin forming Na+F, the single 3s electron from Na is transferred to the partially filled valence shell of F Polar and Nonpolar MoleculesTo determine if a molecule is polar, we need to determine if the molecule has polar bondsthe arrangement of these bonds in spaceMolecular dipole moment (m): the vector sum of the individual bond dipole moments in a moleculereported in debyes (D)these molecules have polar bonds, but each has a zero dipole momentthese molecules have polar bonds and are polar moleculesformaldehyde has polar bonds and is a polar molecule ResonanceFor many molecules and ions, no single Lewis structure provides a truly accurate representationLinus Pauling 1930smany molecules and ions are best described by writing two or more Lewis structuresindividual Lewis structures are called contributing structuresconnect individual contributing structures by doubleheaded (resonance) arrowsthe molecule or ion is a hybrid of the various contributing structuresExamples: equivalent contributing structuresCurved arrow: a symbol used to show the redistribution of valence electronsIn using curved arrows, there are only two allowed types of electron redistribution:from a bond to an adjacent atomfrom an atom to an adjacent bondElectron pushing is a survival skill in organic chemistrylearn it well!All contributing structures must1. have the same number of valence electrons2. obey the rules of covalent bondingno more than 2 electrons in the valence shell of H no more than 8 electrons in the valence shell of a 2nd period element3rd period elements, such as P and S, may have up to 12 electrons in their valence shells3. differ only in distribution of valence electrons。orbital overlap pictures of methane, ammonia, and watersp2 Hybrid Orbitalsthe axes of the three sp2 hybrid orbitals lie in a plane and are directed toward the corners of an equilateral trianglethe unhybridized 2p orbital lies perpendicular to the plane of the three hybrid orbitalsBonding in Ethylenesp Hybrid Orbitalstwo lobes of unequal size at an angle of 180176。) C: a carbon bonded to one other carbon1176。 carbonSecondary (2176。 H: a hydrogen bonded to a 2176。) C: a carbon bonded to three other carbons3176。) 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。 to 60176。 all bonds on adjacent carbons are staggered Cyclohexane In a chair conformation, six H are equatorial and six are axial For cyclohexane, there are two equivalent chair conformationsall CH bonds equatorial in one chair are axial in the alternative chair, and vice versa Boat conformation: a puckered conformation of a cyclohexane ring in which carbons 1 and 4 are bent toward each otherthere are four sets of eclipsed CH interactions and one flagpole interaction a boat conformation is less stable than a chair conformation by 27 kJ ( kcal)/mol Twistboat conformationapproximately kJ ( kcal)/mol less stable than a chair conformation approximately kJ ( kcal)/mol more stable than a boat conformation Cis,Trans Isomers 1,2Dimethylcyclopentane 1,4Dimethylcyclohexane trans1,4Dimethylcyclohexanethe diequatorialmethyl chair conformation is more stable by approximately 2 x () = kJ/mol cis1,4Dimethylcyclohexane The decalins Oxidation of AlkanesOxidation is the basis for their use as energy sources for heat and powerCombustion: a reaction with oxygen that takes place at high temperatures and converts alkanes to carbon dioxide and water.heat of bustion: heat released when one mole of a substance in its standard state is oxidized to carbon dioxide and water Heat of bustion for constitutional isomers For constitutional isomers [kJ (kcal)/mol] strain