1、Macintosh PICTimage formatis not supported 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-2M acintosh PIC Tim age form atis not supportedMacintosh
2、PICTimage formatis not supportedMa c i n t o s h P I C Ti ma g e f o r ma ti s n o t s u p p o r t e dMacintosh PICTimage formatis not supportedMaci ntosh PI CTi mage formati s not supported benzene and its derivatives(Ch 21-22)we do not study arenes until Chapters 21&22 however,we show structural f
3、ormulas of compounds containing the phenyl group before that time the phenyl group is not reactive under any of the conditions we describe in Ch 6-20M a c i n t o s h P I C Ti m a g e f o r m a ti s n o t s u p p o r t e duA double bond consists of one sigma bond formed by the overlap of sp2 hybrid
4、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 120 it takes approximately 264 kJ(63 kcal)/mol to break the pi bond in ethylene;that is,to rotate one carbon
5、 by 90 with respect to the other so that there is no overlap between 2p orbitals on adjacent carbons 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 double bondMaci nt osh PI CTi mage f or mati s not
6、suppor t edMacintosh PICTimage formatis not supportedM acintosh PICTim age form atis not supported the sum of the number of rings and pi bonds in a moleculeuTo determine IHD,compare the number of hydrogens in an unknown compound with the number in a reference hydrocarbon of the same number of carbon
7、s and with no rings or pi bonds the molecular formula of the reference hydrocarbon is CnH2n+2 for each atom of a Group 7 element(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),subt
8、ract one hydrogenIDH=2(Hreference -Hmolecule)isopentyl acetate has a molecular 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 acetateM acintosh PICTim age fo
9、rm atis not supported1.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,loc
10、ate the double bond,and name the main chainMacintosh PICTimage formatis not supporteduDespite the precision and universal acceptance of IUPAC nomenclature,some alkenes,particularly low-molecular-weight ones,are known almost exclusively by their common namesMaci ntosh PI CTi mage formati s not suppor
11、ted the common names methylene,vinyl,and allyl are often used to show the presence of the following alkenyl groupsM a c i n t o s h P I C Ti m a g e f o r m a ti s n o t s u p p o r t e duConfiguration is determined by the orientation of atoms of the main chainM a c in to s h P IC Tim a g e fo r m a
12、 tis n o t s u p p o r te d 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)Maci nt osh PI CTi mage f or mati s not suppor t ed name each a
13、lkene and specify its configuration by the E,Z systemMacintosh PICTimage formatis not supporteduCycloalkenes in small-ring cycloalkenes,the configuration of the double bond is cis these rings are not large enough to accommodate a trans double bondMaci nt osh PI CTi mage f ormati s not support ed tra
14、ns-cyclooctene 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 centerMa c i n t o s h P I CTi ma g e f o r ma ti s n
15、 o t s u p p o r t e duFor 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 dienesMaci ntosh PI CTi mage formati s not supported for alkenes with double bonds,each of which c
16、an show cis,trans isomerism,stereoisomers are possible example:22=4 cis,trans isomers are possible for 2,4-heptadieneM acintosh PIC Tim age form atis not supportedM acin to sh P IC Tim ag e fo rm atis n o t su p p o rted vitamin A,a biologically important compound for which a number of cis,trans iso
17、mers is possible there are four double bonds about which cis,trans isomerism is possible,for 24=16 stereoisomersMa c i n t o s h PI CTi ma g e f o r ma ti s n o t s u p p o r t e duAlkenes are nonpolar compoundsuThe only attractive forces between their molecules are dispersion forcesuThe physical pr
18、operties of alkenes are similar to those of alkanes a compound whose carbon skeleton can be divided into two or more units identical with the carbon skeleton of isopreneMaci nt osh PI CTi mage f or mati s not suppor t eduMyrcene,C10H16,a component of bayberry wax and oils of bay and verbenauMenthol,
19、from peppermintM a c in t o s h P IC Tim a g e f o r m a tis n o t s u p p o r t e dM a c i n t o s h P I C Ti m a g e f o r m a ti s n o t s u p p o r t e dM a c in to s h P IC Tim a g e fo rm a tis n o t s u p p o rte dM a c in to s h P IC Tim a g e fo rm a tis n o t s u p p o rte d-Pinene,from tu
20、rpentine camphor,from the camphor treeM a c in to s h P IC Tim a g e fo rm a tis n o t s u p p o rte dM a c in to s h P IC Tim a g e fo rm a tis n o t s u p p o rte dM a c in to s h P IC Tim a g e fo r m a tis n o t s u p p o r te dM acintosh P IC Tim age form atis not supporteduAnimal fats and vege
21、table oils are both triesters of glycerol,hence the name hydrolysis of a triglyceride in aqueous base followed by acidification gives glycerol 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 fat
22、ty acidsMaci nt osh PI CTi mage f or mati s not suppor t ed 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,t
23、he lower the melting point triglycerides rich in unsaturated 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 the four most abundant fatty acidsM a c in t o s h P IC T
24、im a g e f o r m a tis n o t s u p p o r t e d carbon chains of saturated fatty 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 der
25、ived from them are solids at room temperature following is a saturated triglycerideM a c i n t o s h P I C Ti ma g e f o r ma ti s n o t s u p p o r t e d cis double bonds place kinks in the chains of unsaturated fatty acids unsaturated fatty acids and the triglycerides derived from them do not pack
26、 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 temperatureM a c i n t o s h P I C Ti m a g e f o r m a ti s n o t s u p p o r t e d
