有机化学专题知识专家讲座.ppt

2011 Pearson Education,Inc.,Click to edit Master title style,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,2011 Pearson Education,Inc.,Click to edit Master title style,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,2011 Pearson Education,Inc.,Click to edit Master title style,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,2011 Pearson Education,Inc.,有机化学专题知识专家讲座,Carbon-containing compounds were once considered“organ compounds”available only from living organisms.,The synthesis of the simple organic compound urea in 1828 showed that organic compounds can be prepared in the laboratory from non-living material.,Today,organic natural products are routinely synthesized in the laboratory,.,Organic Chemistry,2,Carbon neither gives up nor accepts electrons because it is in the center of the second periodic row.,Consequently,carbon forms bonds with other carbons and other atoms by sharing electrons.,The capacity of carbon to form bonds in this fashion makes it the building block of all living organisms.,Why Carbon?,3,Why Study,Organic Chemistry,?,Since carbon is the building block of all living organisms,a knowledge of,Organic Chemistry,is a prerequisite to understanding,Biochemistry,Medicinal Chemistry,and,Pharmacology,.,Indeed,Organic Chemistry,is a required course for studying,Pharmacy,Medicine,and,Dentistry,.,Admission into these professional programs is highly dependent on your performance in,Organic Chemistry,.,4,Examples of Organic Compounds Used as Drugs,Methotrexate,Anticancer Drug,5-Fluorouracil,Colon Cancer Drug,Tamiflu,Influenza Drug,AZT,HIV Drug,5,Examples of Organic Compounds Used as Drugs,Haldol,Antipsychotic,Elavil,Antidepressant,Prozac,Antidepressant,Viagra,TreatsErectile Dysfunction,6,The Structure of an Atom,An atom consists of electrons,positively charged protons,and neutral neutrons.,Electrons form chemical bonds.,Atomic number:numbers of protons in its nucleus,Mass number:the sum of the protons and neutrons of an atom,Isotopes have the same atomic number but different mass,numbers.,The atomic weight:the average weighted mass of its atoms,Molecular weight:the sum of the atomic weights of all the atoms,in the molecule,7,The Distribution of Electrons in an Atom,Quantum mechanics uses the mathematical equation of wave,motions to characterize the motion of an electron around a,nucleus.,Wave functions or orbitals tell us the energy of the electron and,the volume of space around the nucleus where an electron is,most likely to be found.,The atomic orbital closer to the nucleus has the lowest energy.,Degenerate orbitals have the same energy.,8,9,The ground-state electronic configuration describes the orbitals,occupied by the atoms electrons with the lowest energy,10,The Aufbau principle:an electron always goes to the,available orbital with the lowest energy,The Pauli exclusion principle:only two electrons can,occupy one atomic orbital and the two electrons have,opposite spin,Hunds rule:electrons will occupy empty degenerated,orbitals before pairing up in the same orbital,The following principles determine which orbitals,electrons occupy:,11,Lewiss theory:an atom will give up,accept,or share electrons in,order to achieve a filled outer shell or an outer shell that contains,eight electrons,12,Ionic Bonds Are Formed by the Transfer of Electrons,Attractive forces between opposite charges are called electrostatic,attractions,13,Covalent Bonds Are Formed by Sharing Electrons,14,15,Equal sharing of electrons:nonpolar covalent bond,(e.g.,H,2,),Sharing of electrons between atoms of different,electronegativities:polar covalent bond(e.g.,HF),16,A polar covalent bond has a slight positive charge on one,end and a slight negative charge on the other,17,18,A Polar Bond Has a Dipole Moment,A polar bond has a negative end and a positive end,dipole moment(D)=,m,=,e,x,d,(,e,):magnitude of the charge on the atom,(,d,):distance between the two charges,19,Electrostatic Potential Maps,20,Lewis Structure,Formal charge=,number of valence electrons,(number of lone pair electrons+1/2 number of bonding electrons,),21,Nitrogen has five valence electrons,Carbon has four valence electrons,Hydrogen has one valence electron and halogen has,seven,22,Important Bond Numbers,Neutral,Cationic,Anionic,23,Non-Octet Species,Sulfuric Acid,Periodic Acid,Phosphoric Acid,In the 3rd and 4th rows,expansion beyond the octet to 10 and 12 electrons is possible.,Reactive species without an octet such as radicals,carbocations,carbenes,and electropositive atoms(boron,beryllium).,Nitric Oxide Radical,Mammalian Signaling Agent,Radical,Carbocation,Carbene,Borane,24,25,The,s,Orbitals,An orbital tells us the volume of space around the nucleus,where an electron is most likely to be found,26,The,p,Orbitals,27,Molecular Orbitals,Molecular orbitals belong to the whole molecule.,s,bond:formed by overlapping of two,s,orbitals.,Bond strength/bond dissociation:energy required to,break a bond or energy released to form a bond.,28,29,In-phase overlap forms a bonding MO;out-of-phase,overlap forms an antibonding MO:,30,Sigma bond(,s,)is formed by end-on overlap of two,p,orbitals:,A,s,bond is stronger than a,p,bond,31,Pi bond(,p,)is formed by sideways overlap of two parallel,p,orbitals:,32,Bonding in Methane,33,Hybridization of One,s,and Three,p,Orbitals34,The orbitals used in bond formation determine the,bond angles,Tetrahedral bond angle:109.5,Electron pairs spread themselves into space as far from,each other as possible,35,The Bonds in Ethane,36,Hybrid Orbitals of Ethane,37,Bonding in Ethene:A Double Bond,38,Bonding in Ethyne:A Triple Bond,39,Bonding in the Methyl Cation,40,Bonding in the Methyl Radical,41,Bonding in the Methyl Anion,42,Bonding in Water,43,Bonding in Ammonia and in the Ammonium Ion,44,Bonding in Hydrogen Halides,45,Summary,The shorter the bond,the stronger it is,The greater the electron density in the region of orbital,overlap,the stronger is the bond,The more,s,character,the shorter and stronger is the,bond,The more,s,character,the larger is the bond angle,46,The vector sum of the magnitude and the direction of the individual,bond dipole determines the overall dipole moment of a molecule,Molecular Dipole Moment,47,BrnstedLowry Acids and Bases,Acid donates a proton,Base accepts a proton,Strong reacts to give weak,The weaker the base,the stronger is its conjugate acid,Stable bases are weak bases,48,An Acid/Base Equilibrium,K,a,:,The acid dissociation constant.,The stronger the acid,the larger its,K,a,value and the smaller its p,K,a,value.,49,The Most Common Organic Acids Are Carboxylic Acids,50,51,Protonated alcohols and protonated carboxylic acids are,very strong acids,52,An amine can behave as an acid or as a base,53,54,Strong Acids/Bases React to Form Weak Acids/Bases,55,The Structure of an Acid Affects Its Acidity,The weaker the base,the stronger is its conjugate,acid,Stable bases are weak bases,The more stable the base,the stronger is its conjugate,acid,56,The stability of a base is affected by its size and its,electronegativity,57,58,When atoms are very different in size,the stronger,acid will have its proton attached to the largest atom,size overrides electronegativity,59,When atoms are similar in size,the stronger acid will,have its proton attached to the more electronegative,atom,60,Substituents Affect the Strength of an Acid,61,Inductive electron withdrawal increases the acidity of aconjugate acid,62,Acetic acid is more acidic than ethanol,The delocalized electrons in acetic acid are shared by,more than two atoms,thereby stabilizing the conjugated,base,63,A Summary of the Factors That Determine Acid Strength,Size:As the atom attached to the hydrogen increases,in size,the strength of the acid increases,2.Electronegativity,64,3.Hybridization,4.Inductive effect,65,5.Electron delocalization,66,Lewis acid:non-proton-donating acid;will accept two,electrons,Lewis base:electron pair donors,Lewis Acids and Bases,67,Basicity and Drug Design:Methotrexate,Substituting Nitrogen for Oxygen,68,Acidity and Cosmetics:Skin Peel Agents,Skin Peels:Remove old skin with an acid to expose new young-looking skin.,The stronger the acid,the deeper the peel.,Examples of skin peel agents:,Deep Peel Agent:,Mild Peel Agents:,69,