6 CHAPTER 1 Structure and Properties of Organic Compounds (b)There is no charge on the formaldehyde molecule,because the 12 electrons in the structure equals the number of valence electrons-that is,6 for O.4 for C,and 2 for two H's. (c)This species is neutral,because there are 13 electrons shown in the formula and 13 valence electrons: 8 from two C's and 5 from five H's. (d)There are 15 valence electrons:6 fromO.5 from N.and 4 from four H's.The Lewis dot structure shows 14 electrons.It has a charge of 15-14=+1 and is the hydroxylammonium cation.[H,NOH]. (e)There are 25 valence electrons,21 from three Cl's and 4 from C.The Lewis dot formula shows 26electrons. It has a charge of 25 -26 =-I and is the trichloromethide anion.:CCl. 1.3 Types of Bonds Covalent bonds,the mainstays of organic compounds,are formed by the sharing of pairs of electrons.Sharing can occur in two ways: 1)A,+,B4A·B In method (1),each atom brings an electron for the sharing.In method (2),the donor atom (B:)brings both electrons to the"marriage"with the acceptor atom(A):in this case,the covalent bond is termed a coordinate covalent bond e me mar he新 n he th ise by alant hond (a)NHj:(b)BF(c)(CH),OMgCl:and (d)Fe(CO)s acceptor (a)H+ +:NH3 NH+(All N-H bonds are alike.) (b)F3B +:月： BF (All B-F bonds are alike.) (o):g-Mg-:+:0-CH, →(CH326-MgC12 CH: (d)Fe +5:C=0: →Fe(C=O)5 Notice that in each of the products there is at least one element that does not have its usual covalence-this is typical of coordinate covalent bonding. Rcnm心o@二ooe5边o总t品h器co bonds,it some Problem 1.10 Show how the ionic compound Li'F-forms from atoms of Li and F. Li.+.F:Lit:F:(or simply LiF) 1.4 Functional Groups Hydrocarbons contain only Cand hydrogen(H).H's in hydrocarbons can be replaced by other atoms or groups ctional group nmolecules.The al groups ne common onal groups are given n Table 13 (b) There is no charge on the formaldehyde molecule, because the 12 electrons in the structure equals the number of valence electrons—that is, 6 for O, 4 for C, and 2 for two H’s. (c) This species is neutral, because there are 13 electrons shown in the formula and 13 valence electrons: 8 from two C’s and 5 from five H’s. (d) There are 15 valence electrons: 6 from O, 5 from N, and 4 from four H’s. The Lewis dot structure shows 14 electrons. It has a charge of 15 14 1 and is the hydroxylammonium cation, [H3NOH]. (e) There are 25 valence electrons, 21 from three Cl’s and 4 from C. The Lewis dot formula shows 26 electrons. It has a charge of 25 26 1 and is the trichloromethide anion, :CCl– 3 . 1.3 Types of Bonds Covalent bonds, the mainstays of organic compounds, are formed by the sharing of pairs of electrons. Sharing can occur in two ways: 6 CHAPTER 1 Structure and Properties of Organic Compounds (1) A ⋅+⋅B → A:B (2) A + :B → A : B coordinate covalent acceptor donor In method (1), each atom brings an electron for the sharing. In method (2), the donor atom (B:) brings both electrons to the “marriage” with the acceptor atom (A); in this case, the covalent bond is termed a coordinate covalent bond. Problem 1.9 Each of the following molecules and ions can be thought to arise by coordinate covalent bond￾ing. Write an equation for the formation of each one and indicate the donor and acceptor molecule or ion: (a) NH 4 ; (b) BF 4 ; (c) (CH3 )2 OMgCl2 ; and (d) Fe(CO)5 . Notice that in each of the products there is at least one element that does not have its usual covalence—this is typical of coordinate covalent bonding. Recall that an ionic bond results from a transfer of electrons (M·  A· M  :A). Although C usually forms covalent bonds, it sometimes forms an ionic bond (see Section 3.2). Other organic ions, such as CH3 COO (acetate ion), have charges on heteroatoms. Problem 1.10 Show how the ionic compound LiF forms from atoms of Li and F. These elements react to achieve a stable noble-gas electron configuration (NGEC). Li(3) has one electron more than He and loses it. F(9) has one electron less than Ne and therefore accepts the electron from Li. (a) (b) (c) (d) 1.4 Functional Groups Hydrocarbons contain only C and hydrogen (H). H’s in hydrocarbons can be replaced by other atoms or groups of atoms. These replacements, called functional groups, are the reactive sites in molecules. The C-to-C double and triple bonds are considered to be functional groups. Some common functional groups are given in Table 1.3.