1、Organic ChemistryUnsaturated Hydrocarbons contains one or more carbon-carbon double or triple bonds contains a carbon-carbon double bond and has the general formula CnH2n contains a carbon-carbon triple bond and has the general formula CnH2n-2 Ethylene(an alkene)H HC CC CH HH HH H Acetylene(an alkyn
2、e).H-CH-CC-HC-HUnsaturated Hydrocarbons benzene and its derivatives(Ch 21-22)we do not study arenes until Chapters 21&22 however,we show structural formulas of compounds containing the phenyl group before that time the phenyl group is not reactive under any of the conditions we describe in Ch 6-20B
3、Be en nz ze en ne eA A l lt te er rn na at ti iv ve e r re ep pr re es se en nt ta at ti io on ns s f fo or r t th he e p ph he en ny yl l g gr ro ou up pC CC CC CC CC CC CC C6 6H H5 5-P Ph h-H HH HH HH HH HH HStructure of AlkenesuA double bond consists of one sigma bond formed by the overlap of sp2
4、 hybrid orbitals and one pi bond formed by the overlap of parallel 2p orbitals the two carbon atoms of a double bond and the four atoms bonded to them lie in a plane,with bond angles of approximately 120Structure of Alkenes it takes approximately 264 kJ(63 kcal)/mol to break the pi bond in ethylene;
5、that is,to rotate one carbon by 90 with respect to the other so that there is no overlap between 2p orbitals on adjacent carbons Isomerism in Alkenes 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 carbon-carbon do
6、uble bondc ci is s-2 2-B Bu ut te en ne em m p p -1 13 39 9 C C,b bp p 4 4 C Ct tr ra an ns s-2 2-B Bu ut te en ne em m p p -1 10 06 6 C C,b bp p 1 1 C CC CC CC CH H3 3H HH H3 3C CH HC CC CH HC CH H3 3H H3 3C CH HIndex of Hydrogen Deficiency the sum of the number of rings and pi bonds in a moleculeu
7、To determine IHD,compare the number of hydrogens in an unknown compound with the number in a reference hydrocarbon of the same number of carbons and with no rings or pi bonds the molecular formula of the reference hydrocarbon is CnH2n+2Index of Hydrogen Deficiency for each atom of a Group 7 element(
8、F,Cl,Br,I),add one H no correction is necessary for the addition of atoms of Group 6 elements(O,S)to the reference hydrocarbon for each atom of a Group 5 element(N,P),subtract one hydrogenIDH=IDH=2 2(H(Hreferencereference -H -Hmoleculemolecule)Index of Hydrogen Deficiency isopentyl acetate has a mol
9、ecular formula of C7H14O2.Calculate its IHD reference hydrocarbon C7H16 IHD=(16-14)/2=1 calculate the IHD for niacin,molecular formula C6H6N2O reference hydrocarbon C6H16 IHD=(16-6)/2=5OOIsopentyl acetateIsopentyl acetateN NN N H H2 2O ON iacinN iacinIUPAC Nomenclature1.Number the longest chain of c
10、arbon 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 chain1 1-H H e
11、 ex xe en ne e4 4-M M e et th hy yl l-1 1-h he ex xe en ne e2 2-E Et th hy yl l-4 4-m m e et th hy yl l-1 1-p pe en nt te en ne e1 12 23 34 45 56 61 12 23 34 45 56 61 12 23 34 45 5Common NamesuDespite the precision and universal acceptance of IUPAC nomenclature,some alkenes,particularly low-molecula
12、r-weight ones,are known almost exclusively by their common namesC C H H2 2=C C H H2 2C C H H3 3C C H H=C C H H2 2C C H H3 3C C=C C H H2 2P Pr ro op py yl l e en ne eE Et th hy yl l e en ne eC C o om m m m o on n:I IU UP PA A C C:2 2-M M e et th hy yl l p pr ro op pe en ne eP Pr ro op pe en ne eE Et
13、th he en ne eI Is so ob bu ut ty yl l e en ne eC C H H3 3Common Names the common names methylene,vinyl,and allyl are often used to show the presence of the following alkenyl groupsCH2=CH2=CH-CH2=CHCH2H2CCH2=CHCH2=CHCH2A A l ll ly yl lM M e et th hy yl li id de en ne ec cy yc cl lo op pe en nt ta an
14、ne e(M M e et th hy yl le en ne ec cy yc cl lo op pe en nt ta an ne e)E Et th he en ny yl l c cy yc cl lo op pe en nt ta an ne e(V V i in ny yl lc cy yc cl lo op pe en nt ta an ne e)V V i in ny yl lM M e et th hy yl le en ne eE Ex xa am m p pl le eC C o om m m m o on n N N a am m e eA A l lk ke en n
15、y yl lG G r ro ou up pM M e et th hy yl li id de en ne eE Et th he en ny yl l3 3-P Pr ro op pe en ny yl l3 3-P Pr ro op pe en ny yl lc cy yc cl lo op pe en nt ta an ne e(A A l ll ly yl lc cy yc cl lo op pe en nt ta an ne e)I IU U P PA A C C N N a am m e e(C C o om m m m o on n n na am m e e)The,Syst
16、emuConfiguration is determined by the orientation of atoms of the main chainC CH HC CC CH H3 3C CH H(C CH H3 3)2 2H H3 3C CC CH HC CC CH H2 2C CH H3 3H HC CH H3 3C CH H2 2c ci is s-3 3,4 4-D D i im m e et th hy yl l-2 2-p pe en nt te en ne e1 12 23 34 4t tr ra an ns s-3 3-H H e ex xe en ne eThe,Syst
17、em uses priority rules(Chapter 3)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,entgegen)Z Z (z zu us sa am m m m e en n)E E (e en nt tg ge eg ge en n)C Ch hi ig gh he er rC Ch
18、hi ig gh he er rl lo ow w e er rl lo ow w e er rC Cl lo ow w e er rh hi ig gh he er rC Cl lo ow w e er rh hi ig gh he er rThe,System name each alkene and specify its configuration by the E,Z system(a)(a)(b)(b)(d)(d)(c)(c)C C l lC C l lB Br rC C l l IsomerismuCycloalkenes in small-ring cycloalkenes,t
19、he configuration of the double bond is cis these rings are not large enough to accommodate a trans double bondC C y yc cl lo oh he ep pt te en ne eC Cy yc cl lo oh he ex xe en ne eC C y yc cl lo op pe en nt te en ne eH HH HH HH HH HH HH HH HC C y yc cl lo ob bu ut te en ne e Isomerism trans-cyclooct
20、ene is the smallest trans cyclooctene that has been prepared in pure form and is stable at room temperature the cis isomer is 38 kJ(9.1 kcal)/mol more stable than the trans isomer the trans isomer is chiral even though it has no chiral centert rans-t rans-C ycl oocteneC ycl ooctene(a pai r of enanti
21、 om ers)(a pai r of enanti om ers)Dienes,Trienes,and PolyenesuFor alkenes containing two or more double bonds,change the infix-to-,-,etc.those containing several double bonds are often referred more generally as polyenes following are three dienes1 1,4 4-P Pe en nt ta ad di ie en ne e2 2-M M e et th
22、 hy yl l-1 1,3 3-b bu ut ta ad di ie en ne e (I Is so op pr re en ne e)1 1,3 3-C C y yc cl lo op pe en nt ta ad di ie en ne eDienes,Trienes,and Polyenes for alkenes with double bonds,each of which can show cis,trans isomerism,stereoisomers are possible example:22=4 cis,trans isomers are possible for
23、 2,4-heptadieneC C2 2-C C3 3C C4 4-C C5 5D D o ou ub bl le e b bo on nd dt tr ra an ns st tr ra an ns st tr ra an ns sc ci is sc ci is st tr ra an ns sc ci is sc ci is s(2 2E E,4 4E E)-2 2,4 4-H H e ep pt ta ad di ie en ne e(2 2E E,4 4Z Z)-2 2,4 4-H H e ep pt ta ad di ie en ne e1 12 23 34 45 56 67 7
24、2 24 42 24 42 24 4(2 2Z Z,4 4E E)-2 2,4 4-H H e ep pt ta ad di ie en ne e(2 2Z Z,4 4Z Z)-2 2,4 4-H H e ep pt ta ad di ie en ne eDienes,Trienes,and Polyenes vitamin A,a biologically important compound for which a number of cis,trans isomers is possible there are four double bonds about which cis,tran
25、s isomerism is possible,for 24=16 stereoisomersC CH H2 2O O H HV V i it ta am m i in n A A (r re et ti in no ol l)Physical PropertiesuAlkenes are nonpolar compoundsuThe only attractive forces between their molecules are dispersion forcesuThe physical properties of alkenes are similar to those of alk
26、anesTerpenes a compound whose carbon skeleton can be divided into two or more units identical with the carbon skeleton of isoprene2 2-M M e et th hy yl l-1 1,3 3-b bu ut ta ad di ie en ne e (I Is so op pr re en ne e)1 12 23 34 4h he ea ad dt ta ai il lTerpenesuMyrcene,C10H16,a component of bayberry
27、wax and oils of bay and verbenauMenthol,from peppermintO O H HTerpenes -Pinene,from turpentine camphor,from the camphor treeO OFatty AcidsuAnimal fats and vegetable oils are both triesters of glycerol,hence the name hydrolysis of a triglyceride in aqueous base followed by acidification gives glycero
28、l and three fatty acids fatty acids with no C=C double bonds are called saturated fatty acid those with one or more C=C double bonds are called unsaturated fatty acidsO OC CH H2 2O O C CR RC CH H2 2O O C CR R R R C CO O C CH HO OO O1 1.N Na aO O H H,H H2 2O O2 2.H H C Cl l,H H2 2O OC CH H2 2O O H HC
29、 CH H2 2O O H HH HO O C CH HR RC CO OO O H HR R C CO O O O H HR R C CO O O O H HA A t tr ri ig gl ly yc ce er ri id de e(a a t tr ri ie es st te er r o of f g gl ly yc ce er ro ol l)1 1,2 2,3 3-P Pr ro op pa an ne et tr ri io ol l(G G l ly yc ce er ro ol l)+F Fa at tt ty y a ac ci id ds sFatty Acids
30、 the most common fatty acids have an even number of carbons,and between 12 and 20 carbons in an unbranched chain the C=C double bonds in almost all naturally occurring fatty acids have a cis configuration the greater degree of unsaturation,the lower the melting point triglycerides rich in unsaturate
31、d fatty acids are generally liquid at room temperature and are called triglycerides rich in saturated fatty acids are generally semisolids or solids at room temperature and are called Fatty Acids the four most abundant fatty acidsC CO O O O H HC CO O O O H HC CO O O O H HC CO O O O H HS St te ea ar
32、ri ic c a ac ci id d (1 18 8:0 0)(m m p p 7 70 0 C C)O O l le ei ic c a ac ci id d (1 18 8;1 1)(m m p p 1 16 6 C C)L Li in no ol le ei ic c a ac ci id d (1 18 8:2 2)(m m p p-5 5 C C)L Li i n no ol le en ni ic c a ac ci id d (1 18 8:3 3)(m m p p -1 11 1 C C)Fatty Acids carbon chains of saturated fatt
33、y acids exist largely in the staggered,anti-conformation because of their high degree of order,they pack together well and are held together by dispersion forces as a result both saturated fatty acids and triglycerides derived from them are solids at room temperature following is a saturated triglyc
34、erideFatty Acids cis double bonds place kinks in the chains of unsaturated fatty acids unsaturated fatty acids and the triglycerides derived from them do not pack as well in a crystal lattice as their saturated counterparts,and have weaker dispersion forces between their molecules butter fat,for example,has a high content of saturated fatty acids and is a solid at room temperature salad oils(from plant oils)have a high content of polyunsaturated fatty acids and are liquid at room temperatureAlkenes:Structure andNomenclature
