5.4 Naming Stereoisomeric Alkenes by the E-Z Notational System trans-2-Butene p orbitals perpendicular. Worst geometry for I bond formation Optimal ry for rt bond formation π bond fo IGURE 5.2 Interconversion of cis-and trans-2-butene proceeds by cleavage of the com- ponent of the double bond. The red balls represent the two methyl groups. 5.4 NAMING STEREOISOMERIC ALKENES BY THE E-Z NOTATIONAL SYSTEM When the groups on either end of a double bond are the same or are structurally simi- lar to each other, it is a simple matter to describe the configuration of the double as cis or trans. Oleic acid, for example, a material that can be obtained from olive oil has a cis double bond. Cinnamaldehyde, responsible for the characteristic odor of cin n. has a trans double bond. CH3(CH2)CH CH(CH2)CO2H C6H5 H H H Oleic acid Cinnamaldehyde PROBLEM 5.5 Female houseflies attract males by sending a chemical signal known as a pheromone. The substance emitted by the female housefly that attracts the male has been identified as cis-9-tricosene, C23Ha6. Write a structural formula, including stereochemistry, for this compound The terms"cis" and"trans are ambiguous, however, when it is not obvious which substituent on one carbon is "similar"or "analogous to a reference substituent on the other. Fortunately, a completely unambiguous system for specifying double bond stereo- chemistry has been developed based on an atomic number criterion for ranking sub stituents on the doubly bonded carbons. When atoms of higher atomic number are on the same side of the double bond, we say that the double bond has the Z configuration, where Z stands for the German word zusammen, meaning "together. When atoms of higher atomic number are on opposite sides of the double bond, we say that the config- uration is E. The symbol E stands for the German word entgegen, meaning"opposite Back Forward Main MenuToc Study Guide ToC Student o MHHE Website5.4 NAMING STEREOISOMERIC ALKENES BY THE E–Z NOTATIONAL SYSTEM When the groups on either end of a double bond are the same or are structurally simi￾lar to each other, it is a simple matter to describe the configuration of the double bond as cis or trans. Oleic acid, for example, a material that can be obtained from olive oil, has a cis double bond. Cinnamaldehyde, responsible for the characteristic odor of cin￾namon, has a trans double bond. PROBLEM 5.5 Female houseflies attract males by sending a chemical signal known as a pheromone. The substance emitted by the female housefly that attracts the male has been identified as cis-9-tricosene, C23H46. Write a structural formula, including stereochemistry, for this compound. The terms “cis” and “trans” are ambiguous, however, when it is not obvious which substituent on one carbon is “similar” or “analogous” to a reference substituent on the other. Fortunately, a completely unambiguous system for specifying double bond stereo￾chemistry has been developed based on an atomic number criterion for ranking sub￾stituents on the doubly bonded carbons. When atoms of higher atomic number are on the same side of the double bond, we say that the double bond has the Z configuration, where Z stands for the German word zusammen, meaning “together.” When atoms of higher atomic number are on opposite sides of the double bond, we say that the config￾uration is E. The symbol E stands for the German word entgegen, meaning “opposite.” C6H5 H CH O C H C Oleic acid Cinnamaldehyde CH3(CH2)6CH2 CH2(CH2)6CO2H C H H C 5.4 Naming Stereoisomeric Alkenes by the E–Z Notational System 173 trans-2-Butene p orbitals aligned: Optimal geometry for π bond formation cis-2-Butene p orbitals aligned: Optimal geometry for π bond formation p orbitals perpendicular: Worst geometry for π bond formation FIGURE 5.2 Interconversion of cis- and trans-2-butene proceeds by cleavage of the  com￾ponent of the double bond. The red balls represent the two methyl groups. Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website