CHAPTER 1 Structure and Properties of Organic Compounds 7 es havine similar operties with increasing molecular weight. Problem 1.11 Methane.CH:ethane.C.H:and propane,C.Hs are the first three members of the alkane homologous series.By what structural unit does each member differ from its predecessor These members differ by aCand two H's;the unit is-CH-(a methylene group) Problem 1.12 (a)Write possible Lewis structural formulas for (1)CH,O:(2)CH,O:(3)CH,O:(4)CH N: and (5)CH,SH.(b)Indicate and name the functional group in each case. The atom with the higher valence is usually the one to which most of the other atoms are bonded H H (a)()H -0-H2② =ǒ：3)H (4)H -H (5)H-C -SH (b)(I)一9H (2) =6:3)-C6-H4)-NH2 (⑤)一3 alcohol aldchyde carboxylic acid amine thiol 1.5 Formal Charge The formal charge on a coval 1 atom equals the numk er of ence el nof the unb onded atom (h of sha us the t The sun in a molecule equals the charge on the species.In this outline.formal charges and actual ionic charges (e.g..Na) are both indicated by the signs and Problem 1 13 Determine the formal charge on each atom in the following species:(a)H NBF:(b)CH NH nd (c)SO2 H: (a) H一Nt一B一： :F: GRR-「+2a]-a :atoms The sum of all formal charges equals the charge on the species.In this case.the +1 on N and the-1 on B cancel HH (b例Compounds with the same functional group form a homologous series having similar characteristic chemical properties and often exhibiting a regular gradation in physical properties with increasing molecular weight. Problem 1.11 Methane, CH4; ethane, C2H6; and propane, C3H8, are the first three members of the alkane homologous series. By what structural unit does each member differ from its predecessor? These members differ by a C and two H’s; the unit is —CH2 — (a methylene group). Problem 1.12 (a) Write possible Lewis structural formulas for (1) CH4O; (2) CH2O; (3) CH2O2; (4) CH5N; and (5) CH3 SH. (b) Indicate and name the functional group in each case. The atom with the higher valence is usually the one to which most of the other atoms are bonded. CHAPTER 1 Structure and Properties of Organic Compounds 7 1.5 Formal Charge The formal charge on a covalently bonded atom equals the number of valence electrons of the unbonded atom (the group number) minus the number of electrons assigned to the atom in its bonded state. The assigned number is one half the number of shared electrons plus the total number of unshared electrons. The sum of all formal charges in a molecule equals the charge on the species. In this outline, formal charges and actual ionic charges (e.g., Na) are both indicated by the signs  and . Problem 1.13 Determine the formal charge on each atom in the following species: (a) H3 NBF3 ; (b) CH3 NH 3 ; and (c) SO2 4 . (a) (b) The sum of all formal charges equals the charge on the species. In this case, the 1 on N and the 1 on B cancel (b) (a)