5.2 Structure and Bonding in Alkenes IGURE 5.1(a)The 117.2° framework of o bonds in eth √134 six atoms are coplanar. The arbon -carbon bond is a double bond made up of the 110 pm T component illustrated in b (b) The p orbitals of two hybridized carbons overlap to produce a t bond. An electron pair in the t bond is shared by the two carbons The double bond in ethylene is stronger than the C-C single bond in ethane, but The simplest arithmetic ap. it is not twice as strong. The C=C bond energy is 605 kJ/mol (144.5 kcal/mol) in eth- proach subtracts the C-c ylene versus 368 kJ/mol(88 kcal/mol)for the C-C bond in ethane Chemists do not bond energy of ethane (368 agree on exactly how to apportion the total C-C bond energy between its o and T com- C-c bond energy of ethyl ponents, but all agree that the T bond is weaker than the o bond There are two different types of carbon-carbon bonds in propene, CH3 CH=CH2. kcal/mol). This gives a value The double bond is of the o+ type, and the bond to the methyl group is a o bond of/mol (56 5 kcal/mol) formed by sp'-sp- overlap H sp hybridized carbon H C=C C-C bond length= 150 pm C=C bond length= 134 pm H H PROBLEM 5.3 We can use bond-line formulas to represent alkenes in much the same way that we use them to represent alkanes. Consider the following alkene (a) what is the molecular formula of this alkene? (b)What is its IUPAC name (c)How many carbon atoms are sp-hybridized in this alkene? How many are sp hyb (d)How many o bonds are of the sp2-sp' type? How many are of the sp -sp3 type? SAMPLE SOLUTION (a) Recall when writing bond-line formulas for hydrocar bons that a carbon occurs at each end and at each bend in a carbon chain the appropriate number of hydrogens are attached so that each carbon has four bonds. thus the compound shown is CH3 CH=C(CH, CH3)2 Back Forward Main MenuToc Study Guide ToC Student o MHHE WebsiteThe double bond in ethylene is stronger than the C±C single bond in ethane, but it is not twice as strong. The CœC bond energy is 605 kJ/mol (144.5 kcal/mol) in eth￾ylene versus 368 kJ/mol (88 kcal/mol) for the C±C bond in ethane. Chemists do not agree on exactly how to apportion the total CœC bond energy between its and  com￾ponents, but all agree that the  bond is weaker than the bond. There are two different types of carbon–carbon bonds in propene, CH3CHœCH2. The double bond is of the  type, and the bond to the methyl group is a bond formed by sp3 –sp2 overlap. PROBLEM 5.3 We can use bond-line formulas to represent alkenes in much the same way that we use them to represent alkanes. Consider the following alkene: (a) What is the molecular formula of this alkene? (b) What is its IUPAC name? (c) How many carbon atoms are sp2 -hybridized in this alkene? How many are sp3 - hybridized? (d) How many  bonds are of the sp2 –sp3 type? How many are of the sp3 –sp3 type? SAMPLE SOLUTION (a) Recall when writing bond-line formulas for hydrocar￾bons that a carbon occurs at each end and at each bend in a carbon chain. The appropriate number of hydrogens are attached so that each carbon has four bonds. Thus the compound shown is CH3CH2CHœC(CH2CH3)2 H H H C H H H C±C bond length  150 pm CœC bond length  134 pm sp3 hybridized carbon C C sp2 hybridized carbon 5.2 Structure and Bonding in Alkenes 171 FIGURE 5.1 (a) The framework of  bonds in eth￾ylene showing bond dis￾tances in picometers and bond angles in degrees. All six atoms are coplanar. The carbon–carbon bond is a double bond made up of the  component shown and the  component illustrated in b. (b) The p orbitals of two sp2 hybridized carbons overlap to produce a  bond. An electron pair in the  bond is shared by the two carbons. The simplest arithmetic ap￾proach subtracts the C±C bond energy of ethane (368 kJ/mol; 88 kcal/mol) from the CœC bond energy of ethyl￾ene (605 kJ/mol; 144.5 kcal/mol). This gives a value of 237 kJ/mol (56.5 kcal/mol) for the  bond energy. 117.2 134 pm 110 pm 121.4 (a) (b) Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website