CHAPTER ONE Chemical Bonding 1. 8 CONSTITUTIONAL ISOMERS In the introduction we noted that both Berzelius and wohler were fascinated by the fact isomer"is derived from the that two different compounds with different properties, ammonium cyanate and urea, pos- Greek word meros, meaning sessed exactly the same molecular formula, CH4N2O. Berzelius had studied examples of part,"share,or"por- imilar phenomena earlier and invented the word isomer to describe different compounds om Greek(isos, " the that have the same molecular formula e"). Thus ers are dif. We can illustrate isomerism by referring to two different compounds, nitromethane and methyl nitrite, both of which have the molecular formula Ch3, Nitromethane, H used to power race cars, is a liquid with a boiling point of 101C. Methyl nitrite is a gas boiling at C, which when inhaled causes dilation of blood vessels. Isomers that dif- fer in the order in which their atoms are bonded are often referred to as structural iso- mers. A more modern term is constitutional isomer. As noted in the previous section the order of atomic connections that defines a molecule is termed its constitution and we say that two compounds are constitutional isomers if they have the same molecular formula but differ in the order in which their atoms are connected PROBLEM 1.14 There are many more isomers of CH3NO2 other than nitromethane and methyl nitrite Some such as carbamic acid, an intermediate in the commercial preparation of urea for use as a fertilizer, are too unstable to iso- late. Given the information that the nitrogen and both oxygens of carbamic acid are bonded to carbon and that one of the carbon-oxygen bonds is a double bond, write a Lewis structure for carbamic acid PROBLEM 1.15 Write structural formulas for all the constitutionally isomeric compounds having the given molecular formula (c) CaH (b)C3HO SAMPLE SOLUTION (a)Begin by considering the ways in which two carbons and one oxygen may be bonded. There are two possibilities: C-C-o and C-O-C Add the six hydrogens so that each carbon has four bonds and each oxygen two There are two constitutiona lers:ethyl alcohol and dimethyl ether. H-C-C-O-H duced In Chapter 3 another type of isomerism, called stereoisomerism, will be intro- Stereoisomers have the same constitution but differ in the arrangement of atoms Back Forward Main MenuToc Study Guide ToC Student o MHHE Website1.8 CONSTITUTIONAL ISOMERS In the introduction we noted that both Berzelius and Wöhler were fascinated by the fact that two different compounds with different properties, ammonium cyanate and urea, pos￾sessed exactly the same molecular formula, CH4N2O. Berzelius had studied examples of similar phenomena earlier and invented the word isomer to describe different compounds that have the same molecular formula. We can illustrate isomerism by referring to two different compounds, nitromethane and methyl nitrite, both of which have the molecular formula CH3NO2. Nitromethane, used to power race cars, is a liquid with a boiling point of 101°C. Methyl nitrite is a gas boiling at 12°C, which when inhaled causes dilation of blood vessels. Isomers that dif￾fer in the order in which their atoms are bonded are often referred to as structural iso￾mers. A more modern term is constitutional isomer. As noted in the previous section, the order of atomic connections that defines a molecule is termed its constitution, and we say that two compounds are constitutional isomers if they have the same molecular formula but differ in the order in which their atoms are connected. PROBLEM 1.14 There are many more isomers of CH3NO2 other than nitromethane and methyl nitrite. Some, such as carbamic acid, an intermediate in the commercial preparation of urea for use as a fertilizer, are too unstable to iso￾late. Given the information that the nitrogen and both oxygens of carbamic acid are bonded to carbon and that one of the carbon–oxygen bonds is a double bond, write a Lewis structure for carbamic acid. PROBLEM 1.15 Write structural formulas for all the constitutionally isomeric compounds having the given molecular formula. (a) C2H6O (c) C4H10O (b) C3H8O SAMPLE SOLUTION (a) Begin by considering the ways in which two carbons and one oxygen may be bonded. There are two possibilities: C±C±O and C±O±C. Add the six hydrogens so that each carbon has four bonds and each oxygen two. There are two constitutional isomers: ethyl alcohol and dimethyl ether. In Chapter 3 another type of isomerism, called stereoisomerism, will be intro￾duced. Stereoisomers have the same constitution but differ in the arrangement of atoms in space. Dimethyl ether H±C±O±C±H H W W H H W W H Ethyl alcohol H±C±C±O±H H W W H H W W H Nitromethane H±C±N H W W H O O   œ ± Methyl nitrite H±C±O±NœO H W W H 22 CHAPTER ONE Chemical Bonding The suffix -mer in the word “isomer” is derived from the Greek word meros, meaning “part,” “share,” or “por￾tion.” The prefix iso- is also from Greek (isos, “the same”). Thus isomers are dif￾ferent molecules that have the same parts (elemental composition). Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website