In Chapter 6, we study a group of organic cations called

Write and compare the ground-state electron configurations for each pair of elements. (a) Carbon and silicon (b) Oxygen and sulfur (c) Nitrogen and phosphorus

Draw Lewis structures and condensed structural formulas for the four alcohols with the molecular formula C4H10O. Classify each alcohol as primary, secondary, or tertiary

Draw structural formulas for the three secondary amines with the molecular formula C4H11N.

Draw condensed structural formulas for the three ketones with the molecular formula C5H10O.

Draw condensed structural formulas for the two carboxylic acids with the molecular formula C4H8O2

Draw structural formulas for the four esters with the molecular formula C4H8O2

Predict all bond angles for these molecules. (a) CH3OH (b) PF3 (c) H2CO3

Which molecules are polar? For each that is polar, specify the direction of its dipole moment. (a) CH2Cl2 (b) HCN (c) H2O2

Describe the bonding in these molecules in terms of hybridization of C and N, and the types of bonds between carbon and nitrogen, and if there are any lone pairs, describe what type of orbital contains these electrons. (a) CH3CH"CH2 (b) CH3NH2

Draw the contributing structure indicated by the curved arrows. Be certain to show all valence electrons and all formal charges. (a) H C (b) H C CH3 C CH3 O (c) 2 O2 O O O O

Which sets are valid pairs of contributing structures? (a) CH (b) 3 and CH3 C and 2 C1 CH3 C CH3 C O O2 O O O 2 O O 2 O

Estimate the relative contribution of the members in each set of contributing structures. (a) C1 2C (b) 1 C H H C H O C H H HH H C H H H H O O2 O

Draw three contributing structures of the following compound (called guanidine) and state the hybridization of the four highlighted atoms. In which orbitals do the three lone pairs drawn reside? C H H H H N N N H

Write the ground-state electron confi guration for each atom. After each atom is its atomic number in parentheses. (a) Sodium (11) (b) Magnesium (12) (c) Oxygen (8) (d) Nitrogen (7)

Identify the atom that has each ground-state electron confi guration. (a) 1s 2 2s 2 2p 6 3s 2 3p 4 (b) 1s 2 2s 2 2p 4

Defi ne valence shell and valence electron.

How many electrons are in the valence shell of each atom? (a) Carbon (b) Nitrogen (c) Chlorine (d) Aluminum

Judging from their relative positions in the Periodic Table, which atom in each set is the more electronegative? (a) Carbon or nitrogen (b) Chlorine or bromine (c) Oxygen or sulfur

Which compounds have nonpolar covalent bonds, which have polar covalent bonds, and which have ions? (a) LiF (b) CH3F (c) MgCl2 (d) HCl

Using the symbols d2 and d1, indicate the direction of polarity, if any, in each covalent bond. (a) C!Cl (b) S!H (c) C!S (d) P!H

Write Lewis structures for these compounds. Show all valence electrons. None of them contains a ring of atoms. (a) Hydrogen peroxide, H2O2 (b) Hydrazine, N2H4 (c) Methanol, CH3OH

Write Lewis structures for these ions. Show all valence electrons and all formal charges. (a) Amide ion, NH2 2 (b) Bicarbonate ion, HCO3 2 (c) Carbonate ion, CO3 22 (d) Nitrate ion, NO3 2 (e) Formate ion, HCOO2 (f) Acetate ion, CH3COO2

Complete these structural formulas by adding enough hydrogens to complete the tetra-valence of each carbon. Then write the molecular formula of each compound. (a) C C C9C"C9C9C C (b) C9C9C9C9OH (c) O (d) C9C9C9H (e) (f) O C9C9C9OH O C C9C9C9C9NH2 OH OH (g) C9C9C9C9C (h) (i) O C9C9C9C9OH C"C9C9OH C9C9C9C O NH2

Some of these structural formulas are incorrect (i.e., they do not represent a real compound) because they have atoms with an incorrect number of bonds. Which structural formulas are incorrect, and which atoms in them have an incorrect number of bonds? H (a) (b) H H H H9C9C"O9H (d) (e) H H H H9C#C9C9H H H H H H H H H H H9O9C9C9C9O9H Cl H H H9C"C9H (c) H H H H H H9N9C9C9O9H O (f) H9C9C9C9H O (g) (h) H H H H H H H9C9C"C"C9C9H H H H9C#C9C9H

Following the rule that each atom of carbon, oxygen, and nitrogen reacts to achieve a complete outer shell of eight valence electrons, add unshared pairs of electrons as necessary to complete the valence shell of each atom in these ions. Then assign formal charges as appropriate. (a) C (b) H H H H H C O C H H H H H C (c) N H H H H H C C O O

Following are several Lewis structures showing all valence electrons. Assign formal charges in each structure as appropriate. N O O O O O H C H (a) C (b) C C (c) CH H H H H C H H H C C H H H H C H C H C H (d) (e) H (f) H C H H H H

Which statements are true about electronegativity? (a) Electronegativity increases from left to right in a period of the Periodic Table. (b) Electronegativity increases from top to bottom in a column of the Periodic Table. (c) Hydrogen, the element with the lowest atomic number, has the smallest electronegativity. (d) The higher the atomic number of an element, the greater its electronegativity.

Why does fl uorine, the element in the upper right corner of the Periodic Table, have the largest electronegativity of any element?

Arrange the single covalent bonds within each set in order of increasing polarity. (a) C!H, O!H, N!H (b) C!H, B!H, O!H (c) C!H, C!Cl, C!I (d) C!S, C!O, C!N (e) C!Li, C!B, C!Mg

Using the values of electronegativity given in Table 1.5, predict which indicated bond in each set is the more polar and, using the symbols d1 and d2, show the direction of its polarity. (a) CH3!OH or CH3O!H (b) CH3!NH2 or CH3!PH2 (c) CH3!SH or CH3S!H (d) CH3!F or H!F

Identify the most polar bond in each molecule. (a) HSCH2CH2OH (b) CHCl2F (c) HOCH2CH2NH2

Use VSEPR to predict bond angles about each highlighted atom. Cl O O C C (a) (d) (e) (f) C (b) (c) H H H H H H C C H H H C C H H H C H H H C H H HH H H O O N N O

Use VSEPR to predict bond angles about each atom of carbon, nitrogen, and oxygen in these molecules. (a) CH3 ! CH"CH2 CH3 CH3 CH2 (b) CH (c) 3 N CH3 C OH O (d) H2C"C"CH2 (e) H2C"C"O (f) CH3 ! CH"N ! OH

Use VSEPR to predict the geometry of these ions. (a) NH2 2 (b) NO2 2 (c) NO2 1 (d) NO3 2

Draw Lewis structures for these functional groups. Be certain to show all valence electrons on each. (a) Carbonyl group (b) Carboxyl group (c) Hydroxyl group (d) Ester group (e) Amide group

Draw condensed structural formulas for all compounds with the molecular formula C4H8O that contain (a) A carbonyl group (there are two aldehydes and one ketone). (b) A carbon-carbon double bond and a hydroxyl group (there are eight).

What is the meaning of the term tertiary (3) when it is used to classify alcohols? Draw a structural formula for the one tertiary (3) alcohol with the molecular formula C4H10O

What is the meaning of the term tertiary (3) when it is used to classify amines? Draw a structural formula for the one tertiary (3) amine with the molecular formula C4H11N.

Draw structural formulas for (a) The four primary (1) amines with the molecular formula C4H11N. (b) The three secondary (2) amines with the molecular formula C4H11N. (c) The one tertiary (3) amine with the molecular formula C4H11N

Draw structural formulas for the three tertiary (3) amines with the molecular formula C5H13N.

Draw structural formulas for (a) The eight alcohols with the molecular formula C5H12O. (b) The eight aldehydes with the molecular formula C6H12O. (c) The six ketones with the molecular formula C6H12O. (d) The eight carboxylic acids with the molecular formula C6H12O2. (e) The nine carboxylic esters with the molecular formula C5H10O2

Identify the functional groups in each compound. (a) (b) (c) OH Lactic acid Ethylene glycol CH39CH9C9OH HO9CH29CH29OH O NH2 Alanine CH39CH9C9OH O (d) (e) (f) OH Glyceraldehyde Acetoacetic acid 1,6-Hexanediamine HO9CH29CH9C9H CH39C9CH29C9OH O O O H2NCH2CH2CH2CH2CH2CH2NH2

Draw a three-dimensional representation for each molecule. Indicate which ones have a dipole moment and in what direction it is pointing. (a) CH3F (b) CH2Cl2 (c) CH2ClBr (d) CFCl3 (e) CCl4 (f ) CH2"CCl2 (g) CH2"CHCl (h) HC # C!C # CH (i) CH3C #N ( j) (CH3)2C"O (k) BrCH"CHBr

Tetrafl uoroethylene, C2F4, is the starting material for the synthesis of the polymer polytetrafl uoroethylene (PTFE), one form of which is known as Tefl on. Tetrafl uoroethylene has a dipole moment of zero. Propose a structural formula for this molecule.

Which statements are true about resonance contributing structures? (a) All contributing structures must have the same number of valence electrons. (b) All contributing structures must have the same arrangement of atoms. (c) All atoms in a contributing structure must have complete valence shells. (d) All bond angles in sets of contributing structures must be the same.

Draw the contributing structure indicated by the curved arrow(s). Assign formal charges as appropriate. CH3 (a) H C 2 (b) H C 2 (c) C (d) C (e) H (f) H O O O 2 O O N O O N O O O O O

Using VSEPR, predict the bond angles about the carbon and nitrogen atoms in each pair of contributing structures in Problem 1.52. In what way do these bond angles change from one contributing structure to the other?

In Problem 1.52 you were given one contributing structure and asked to draw another. Label pairs of contributing structures that are equivalent. For those sets in which the contributing structures are not equivalent, label the more important contributing structure.

Are the structures in each set valid contributing structures? N ? (a) C (c) (b) H N ? H N ? C H H (d) C C H H H H H C H H H H C C H H H H H H H H C C H N ? N C O N O? O O O O V

State the orbital hybridization of each highlighted atom. O O O O C C C H H H H C CH2 CH2 C (a) C (d) (e) (f) C (b) (c) H H H H H H H H H H H C HC H H C H (g) (h) (i) H H H C H H H H

Describe each highlighted bond in terms of the overlap of atomic orbitals. C C CH2 C CH2 H H H H (a) (b) H C HC (c) (d) C (e) C (f) H H H H H C H H H O O O H H (g) (h) H C C H (i) H H H H C H H N O O N O O O

Following is a structural formula of the prescription drug famotidine, manufactured by Merck Sharpe & Dohme under the name Pepcid. The primary clinical use of Pepcid is for the treatment of active duodenal ulcers and benign gastric ulcers. Pepcid is a competitive inhibitor of histamine H2 receptors and reduces both gastric acid concentration and the volume of gastric secretions. C O N O H2N H2N N CH2 CC S S CH2 CH2 NH2 N C S NH2 H C (a) Complete the Lewis structure of famotidine showing all valence electrons and any formal positive or negative charges. (b) Describe each circled bond in terms of the overlap of atomic orbitals.

Draw a Lewis structure for methyl isocyanate, CH3NCO, showing all valence electrons. Predict all bond angles in this molecule and the hybridization of each C, N, and O.

What is the hybridization of the highlighted atoms in the following structures, and what are your estimates for the bond angles around these highlighted atoms? In each case, in what kind of orbital does the lone pair of electrons on the nitrogen reside? CH3 CH3 CH3 O H N N CH3 C C C C C C H C N H3C H3C H2C H2C CH2 CH2 H O O

Using cartoon representations, draw a molecular orbital mixing diagram for a C!O s bond. In your picture, consider the relative energies of C and O, and how this changes the resulting bonding and antibonding molecular orbitals relative to a C!C s bond.

In what kind of orbitals do the lone-pair electrons on the oxygen of acetone reside, and are they in the same plane as the methyl !CH3 groups or are they perpendicular to the methyl !CH3 groups?

Draw the delocalized molecular orbitals for the following molecule. Are both p bonds of the triple bond involved in the delocalized orbitals? CH3!C # C!CH"CH2

Why are the following molecular formulas impossible? (a) CH5 (b) C2H7

Each compound contains both ions and covalent bonds. Draw the Lewis structure for each compound, and show by dashes which are covalent bonds and show by charges which are ions. (a) Sodium methoxide, CH3ONa (b) Ammonium chloride, NH4Cl (c) Sodium bicarbonate, NaHCO3 (d) Sodium borohydride, NaBH4 (e) Lithium aluminum hydride, LiAlH4

Predict whether the carbon-metal bond in these organometallic compounds is nonpolar covalent, polar covalent, or ionic. For each polar covalent bond, show the direction of its polarity by the symbols d1 and d2. Tetraethyllead Methylmagnesium chloride Dimethylmercury CH3CH2 CH2CH3 CH2CH3 CH2CH3 (a) (b) (c) Pb CH3 ClMg CH3 Hg CH3

Silicon is immediately under carbon in the Periodic Table. Predict the geometry of silane, SiH4.

Phosphorus is immediately under nitrogen in the Periodic Table. Predict the molecular formula for phosphine, the compound formed by phosphorus and hydrogen. Predict the H!P!H bond angle in phosphine

Draw a Lewis structure for the azide ion, N3 2. (The order of atom attachment is N!N!N, and they do not form a ring.) How does the resonance model account for the fact that the lengths of the N!N bonds in this ion are identical?

Cyanic acid, HOCN, and isocyanic acid, HNCO, dissolve in water to yield the same anion on loss of H1. (a) Write a Lewis structure for cyanic acid. (b) Write a Lewis structure for isocyanic acid. (c) Account for the fact that each acid gives the same anion on loss of H1.

In Chapter 6, we study a group of organic cations called carbocations. Following is the structure of one such carbocation, the tert-butyl cation. C tert-Butyl cation CH3 H3C H3C (a) How many electrons are in the valence shell of the carbon bearing the positive charge? (b) Using VSEPR, predict the bond angles about this carbon. (c) Given the bond angle you predicted in (b), what hybridization do you predict for this carbon?

Many reactions involve a change in hybridization of one or more atoms in the starting material. In each reaction, identify the atoms in the organic starting material that change hybridization, and indicate what the change is. We examine these reactions in more detail later in the course. Cl Cl H C HC C H H H H CC H H H H C O C H H O9H O H C C Cl2 Cl2 (a) (b) H C HC H (d) 2O C H H H H C C H H H C H C H H H C H H H H H O H2O H2 (c) (e) H H H H9C9C9O9C9C9H H H H (f) H H H H C C H H H H C C H Cl H Cl H9C9H O H H9O9C9C9H O H 1.73 Fo

Following is a structural formula of benzene, C6H6, which we study in Chapter 21. H H H H H H C C C C C C (a) Using VSEPR, predict each H!C!C and C!C!C bond angle in benzene. (b) State the hybridization of each carbon in benzene. (c) Predict the shape of a benzene molecule. (d) Draw important resonance contributing structures

Following are three contributing structures for diazomethane, CH2N2. This molecule is used to make methyl esters from carboxylic acids (Section 17.7C). C N N ? N N H H C N H H C H H ? N (a) Using curved arrows, show how each contributing structure is converted to the one on its right. (b) Which contributing structure makes the largest contribution to the hybrid?

(a) Draw a Lewis structure for the ozone molecule, O3. (The order of atom attachment is O!O!O, and they do not form a ring.) Chemists use ozone to cleave carboncarbon double bonds (Section 6.5C).

Draw four contributing resonance structures; include formal charges.

How does the resonance model account for the fact that the length of each O!O bond in ozone (128 pm) is shorter than the O!O single bond in hydrogen peroxide (HOOH, 147 pm) but longer than the O!O double bond in the oxygen molecule (123 pm)?

The following two compounds are isomers, that is, they are different compounds with the same molecular formula. We discuss this type of isomerism in Chapter 5. H C"C Cl H Cl H C"C Cl Cl H (a) Why are these different molecules that do not interconvert? (b) Absorption of light by a double bond in a molecule excites one electron from a p molecular orbital to a p* molecular orbital. Explain how this absorption can lead to interconversion of the two isomers. ?* Energy Light ?*

In future chapters, we will encounter carbanionsions in which a carbon atom has three bonds and a lone pair of electrons and bears a negative charge. Draw another contributing structure for the allyl anion. Now, using cartoon representations, draw the three orbitals that represent the delocalized p system (look at Figure 1.26 for a hint). Which of the three orbitals are populated with electrons? Allyl anion C C C H H H H H

Describe the bonding in PCl5 without using d orbitals. As a hint, the geometry of PCl5 is as shown: Cl Cl Cl Cl Cl P 120 90