(a) Use your molecular models to make ethane, and compare the model with the preceding

(a) Nitrogen has relatively stable isotopes (half-life greater than 1 second) of mass numbers 13, 14, 15, 16, and 17. (All except 14N and 15N are radioactive.) Calculate how many protons and neutrons are in each of these isotopes of nitrogen. (b) Write the electronic configurations of the third-row elements shown in the partial periodic table in Figure 1-6.

Draw Lewis structures for the following compounds. (a) ammonia, NH3 (b) water, H2O (c) hydronium ion, H3O+ (d) propane, C3H8 (e) dimethylamine, CH3NHCH3 (f) diethyl ether, CH3CH2OCH2CH3 (g) 1-chloropropane, CH3CH2CH2Cl (h) propan-2-ol, CH3CH(OH)CH3 (i) borane, BH3 (j) boron trifluoride, BF3 Explain what is unusual about the bonding in the compounds in parts (i) and (j).

Write Lewis structures for the following molecular formulas. (a) N2 (b) HCN (c) HONO (d) CO2 (e) CH3CHNH (f) HCO2H (g) C2H3Cl (h) HNNH (i) C3H6 (one double bond) (j) C3H4 (two double bonds) (k) C3H4 (one triple bond)

Circle any lone pairs (pairs of nonbonding electrons) in the structures you drew for Problem 1-3.

Use electronegativities to predict the direction of the dipole moments of the following bonds. (a) CCl (b) CO (c) CN (d) CS (e) CB (f) NCl (g) NO (h) NS (i) NB (j) BCl

Draw Lewis structures for the following compounds and ions, showing appropriate formal charges. (a) [CH3OH2 ]+ (b) NH4Cl (c) (CH3)4NCl (d) NaOCH3 (e) +CH3 (f) -CH3 (g) NaBH4 (h) NaBH3CN (i) (CH3)2OBF3 (j) [HONH3] + (k) KOC(CH3)3 (l) [H2COH]+

Draw the important resonance forms for the following molecules and ions. (a) CO3 2- (b) H2CCHC + H2 (c) H2CCHC - H2 (d) NO3 - (e) NO2 - (f) H C CH CH CH 2 O (f) (g) [CH3C(OCH3)2 ]+ (h) B(OH)3

For each of the following compounds, draw the important resonance forms. Indicate which structures are major and minor contributors or whether they have the same energy. (a) H2CNN NNC + not significant H H NNC + minor H H NNC + major H H

Draw the important resonance forms of the following cations and anions: (a) CH NH OH CH3O CH CH + (b) +O CH OCH C 3 H H2N CH (c) H2C C OH NH2 CH + (d) H3C CH C CH CNCH O (e) H3C C CH CHCH CN O (f) H2C CH C CH2

Use resonance structures to identify the areas of high and low electron density in the following compounds: (a) \(\mathrm{H}_{2} \mathrm{C}=\mathrm{CH}-\mathrm{NO}_{2}\) (b) \(\mathrm{H}_{2} \mathrm{C}=\mathrm{CH}-\mathrm{C} \equiv \mathrm{N}\) (c) (d) (e) (f) \(\mathrm{CH}_{3} \mathrm{O}-\mathrm{CH}=\mathrm{CH}-\mathrm{CN}\)

Draw complete Lewis structures for the following condensed structural formulas. (a) CH3(CH2)3CH(CH3)2 (b) (CH3)2CHCH2Cl (c) CH3CH2COCN (d) CH2CHCHO (e) (CH3)3CCOCHCH2 (f) CH3COCOOH (g) (CH3CH2)2CO (h) (CH3)3COH

Give Lewis structures corresponding to the following lineangle structures. Give the molecular formula for each structure. (a) N H (b) O (c) N H (d) OH (e) CHO (f) O (g) O (

Repeat Problem 1-11, this time drawing line–angle structures for compounds (a) through (h).

Compute the empirical and molecular formulas for each of the following elemental analyses. In each case, propose at least one structure that fits the molecular formula. C H N Cl MW (a) 40.0% 6.67% 0 0 90 (b) 32.0% 6.67% 18.7% 0 75 (c) 25.6% 4.32% 15.0% 37.9% 93 (d) 38.4% 4.80% 0 56.8% 125

(a) Use your molecular models to make ethane, and compare the model with the preceding structures. (b) Make a model of propane \(\left(\mathrm{C}_{3} \mathrm{H}_{8}\right)\), and draw this model using dashed lines and wedges to represent bonds going back and coming forward.

(a) Predict the hybridization of the oxygen atom in water, \(H_2O\). Draw a picture of its three-dimensional structure, and explain why its bond angle is 104.5\(^{\circ}\). (b) The electrostatic potential maps for ammonia and water are shown here. The structure of ammonia is shown within its EPM. Note how the lone pair creates a region of high electron potential (red), and the hydrogens are in regions of low electron potential (blue). Show how your three-dimensional structure of water corresponds with its EPM.

Predict the hybridization, geometry, and bond angles for the central atoms in (a) but-2-ene, CH3CHCHCH3. (b) CH3CHNH.

Predict the hybridization, geometry, and bond angles for the carbon and nitrogen atoms in acetonitrile (CH3 C N:).

1. Draw a Lewis structure for each compound. 2. Label the hybridization, geometry, and bond angles around each atom other than hydrogen. 3. Draw a three-dimensional representation (using wedges and dashed lines) of the structure. (a) CO2 (b) CH3OCH3 (c) (CH3)3O+ (d) CH3COOH (e) CH3CCH (f) CH3CHNCH3 (g) H2CCO

Allene, CH2 C CH2, has the structure shown below. Explain how the bonding in allene requires the two CH2 groups at its ends to be at right angles to each other. CC H H C H H allene

1. Draw the important resonance forms for each compound. 2. Label the hybridization and bond angles around each atom other than hydrogen. 3. Use a three-dimensional drawing to show where the electrons are pictured to be in each resonance form.

For each pair of structures, determine whether they represent different compounds or a single compound. (a) H and H3C CH2CH3 CH3 H H3C CH2CH3 CH3 H3C CH2CH3 CH3 H3C CH2CH3 CH3 H H H H H and H (b) (c) Br H F Cl C C and Cl F H Br C C (d) Br H H H F Cl C C and F Cl H Br H H

Two compounds with the formula are known. (a) Draw a Lewis structure for this molecule, and label the hybridization of each carbon and nitrogen atom. (b) What two compounds have this formula? (c) Explain why only one compound with the formula is known.

Which of the following compounds show cis-trans isomerism? Draw the cis and trans isomers of those that do. (a) CHFCHF (b) F2CCH2 (c) CH2CHCH2CH3 (d) CHCH3 (e) CHCHCH3 (f) CHCH3

Give the relationship between the following pairs of structures. The possible relationships are: same compound constitutional isomers (structural isomers) cis-trans isomers not isomers (different molecular formula) CH2CH3 CH3CH2CHCH2CH3 CH3 CH3CH2CHCH2CH2CH3 (a) and (b) C C H Br Br H and C C H Br Br H C C H Br Br H and C C H Br H Br (c) (d) C C H Br Br H and C C H Br Br H Cl H Cl Cl Cl H H H H HC C and H HC C (e) (f) CH3 CH3 H CC H and H CC CH3 H CH3 H H H H (g) CH3CH2CH2CH3 and CH3CHCHCH3 (h) CH2CHCH2CH2CH3 and CH3CHCHCH2CH3 (i) CH2CHCH2CH2CH3 and CH3CH2CH2CHCH2 CH3 CH3 and CH3 CH3 (j) CH3 and CH3

Write the electronic configurations for the elements hydrogen through neon. Explain how electronic configurations determine the electronegativities and bonding properties of these elements, and how the third row elements (e.g., Si, P, and S) differ from them. Problems 1-26, 27, 28, and 30

Draw all possible structures corresponding to a given molecular formula. Problems 1-34, 35, and 36

Draw and interpret Lewis, condensed, and line-angle structural formulas. Calculate formal charges. (Problems 1-30, 31, 32, 33, 34, 37, 38, 41, 42, and 45)

Predict patterns of covalent and ionic bonding involving C, H, O, N, and the halogens. Identify resonance-stabilized structures and compare the relative importance of their resonance forms. Problems 1-26, 29, 36, 40, 41, 42, 43, 44, 45, and 46

Calculate empirical and molecular formulas from elemental composition. (Problems 1-47 and 48)

Draw the structure of a single bond, a double bond, and a triple bond. Problems 1-52, 55, 57, and 60

Predict the hybridization and geometry of the atoms in a molecule, and draw a three-dimensional representation of the molecule. Problems 1-49, 51, 52, 53, 56, 57, and 60

Draw the resonance forms of a resonance hybrid, and predict its hybridization and geometry. Predict which resonance form is the major contributor. Problems 1-43, 44, 52, 53, and 54

Identify constitutional isomers and stereoisomers, and predict which compounds can exist as constitutional isomers and as cis-trans (geometric) isomers. Problems 1-49, 56, 58, and 59

(a) Draw the resonance forms for (bonded OSO). (b) Draw the resonance forms for ozone (bonded OOO). (c) Sulfur dioxide has one more resonance form than ozone. Explain why this structure is not possible for ozone

Name the element that corresponds to each electronic configuration. (a) (b) (c) (d)

There is a small portion of the periodic table that you must know to do organic chemistry. Construct this part from memory, using the following steps. (a) From memory, make a list of the elements in the first two rows of the periodic table, together with their numbers of valence electrons. (b) Use this list to construct the first two rows of the periodic table. (c) Organic compounds often contain sulfur, phosphorus, chlorine, bromine, and iodine. Add these elements to your periodic table.

For each compound, state whether its bonding is covalent, ionic, or a mixture of covalent and ionic. (a) NaCl (b) NaOH (c) CH3Li (d) CH2Cl2 (e) NaOCH3 (f) HCO2Na (g) CF4

(a) Both PCl3 and PCl5 are stable compounds. Draw Lewis structures for these two compounds. (b) NCl3 is a known compound, but all attempts to synthesize NCl5 have failed. Draw Lewis structures for NCl3 and a hypothetical NCl5, and explain why NCl5 is an unlikely structure.

Draw a Lewis structure for each species. (a) (b) (c) (d) (e) (f) (g) (h) (i) (j) (k)

Draw a Lewis structure for each compound. Include all nonbonding pairs of electrons. (a) (b) (c) (d)

Draw a lineangle formula for each compound in Problem 1-32.

Draw Lewis structures for (a) two compounds of formula C4H10 (b) two compounds of formula C2H6O (c) two compounds of formula C2H7N (d) three compounds of formula C2H7NO (e) three compounds of formula C3H8O2 (f) three compounds of formula C2H4O

Draw a complete structural formula and a condensed structural formula for (a) three compounds of formula (b) five compounds of formula

Some of the following molecular formulas correspond to stable compounds. When possible, draw a stable structure for each formula. Propose a general rule for the numbers of hydrogen atoms in stable hydrocarbons. CH2 CH3 CH4 CH5 C2H2 C2H3 C2H4 C2H5 C2H6 C2H7 C3H3 C3H4 C3H5 C3H6 C3H7 C3H8 C3H9

Draw complete Lewis structures, including lone pairs, for the following compounds. N (a) pyridine (b) N H pyrrolidine (c) O furan -aminobutyric acid (a neurotransmitter) (d) H2N COOH (e) O N CHO (f) SO3H (g) (h) O O OCH3

Give the molecular formula of each compound shown in Problem 1-37.

1. From what you remember of electronegativities, show the direction of the dipole moments of the following bonds. 2. In each case, predict whether the dipole moment is relatively large (electronegativity difference >0.5) or small. (a) C-Cl (b) C-H (c) C-Li (d) C-N (e) C-O (f) C-B (g) C-Mg (h) N-H (i) O-H (j) C-Br

For each of the following structures, 1. Draw a Lewis structure; fill in any nonbonding electrons. 2. Calculate the formal charge on each atom other than hydrogen. (a) (nitrosomethane) (b) (trimethylamine oxide) (c) (azide ion) (d) (e) (f)

Problem 1.41 Determine whether the following pairs of structures are actually different compounds or simply resonance forms of the same compounds.

Draw the important resonance forms to show the delocalization of charges in the following ions. In each case, indicate the major resonance form(s).

In the following sets of resonance forms, label the major and minor contributors and state which structures would be of equal energy. Add any missing important resonance forms. (a) CH3 CH C N 3 NCCHCH (b) O + 3 CCH CH CH CH3 3 CCH CH CH CH3 O + (c) CH3 C C CH CH3 CH3 C C CH CH3 O O O O (d) CH3 CH CH CH NO2 CH3 CH CH CH NO2 (e) + CH3 2 CCH NH2 CH3 2 CCH NH2

For each of these ions, draw the important resonance forms and predict which resonance form is likely to be the major contributor.

For each pair of ions, determine which ion is more stable. Use resonance forms to explain your answers. (a) CH3 CH CH3 + CH3 CH OCH3 + or (b) + 3 CCH CH3 3 NCH CH3 + 3 CCH CH3 3 CHCH CH3 or (c) CH2 CH CH+ CH3 or CH2 CH CH2 + CH2 (d) CH2 CH3 or 2 NCCH (e) CH2 + CH2 + or (f) O O

Use resonance structures to identify the areas of high and low electron density in the following compounds: (a) (a) CH3 C O H (b) (b) CH3 C O NH2 (c) (c) CH3 C NH H (d) (d) CH3 C O OCH3 (e) (e) CH3O C O NH2 (f) NH O (g) CN NH2 (h) (h) O O (i) O N H (j) H C O CH3O

Compound X, isolated from lanolin (sheeps wool fat), has the pungent aroma of dirty sweatsocks. A careful analysis showed that compound X contains 62.0% carbon and 10.4% hydrogen. No nitrogen or halogen was found. (a) Compute an empirical formula for compound X. (b) A molecular weight determination showed that compound X has a molecular weight of approximately 117. Find the molecular formula of compound X. (c) Many possible structures have this molecular formula. Draw complete structural formulas for four of them.

In 1934, Edward A. Doisy of Washington University extracted 3000 lb of hog ovaries to isolate a few milligrams of pure estradiol, a potent female hormone. Doisy burned 5.00 mg of this precious sample in oxygen and found that 14.54 mg of CO2 and 3.97 mg of H2O were generated. (a) Determine the empirical formula of estradiol. (b) The molecular weight of estradiol was later determined to be 272. Determine the molecular formula of estradiol.

If the carbon atom in CH2Cl2 were flat, there would be two stereoisomers. The carbon atom in CH2Cl2 is actually tetrahedral. Make a model of this compound, and determine whether there are any stereoisomers of CH2Cl2. ClC Cl H H ClC H Cl H

Cyclopropane (C3H6, a three-membered ring) is more reactive than most other cycloalkanes. (a) Draw a Lewis structure for cyclopropane. (b) Compare the bond angles of the carbon atoms in cyclopropane with those in an acyclic (noncyclic) alkane. (c) Suggest why cyclopropane is so reactive.

For each of the following compounds, 1. Give the hybridization and approximate bond angles around each atom except hydrogen. 2. Draw a three-dimensional diagram, including any lone pairs of electrons. (a) H3O+ (b) -OH (c) CH2CHCN (d) (CH3)3N (e) [CH3NH3] + (f) CH3COOH (g) CH3CHNH (h) CH3OH (i) CH2O

For each of the following compounds and ions, 1. Draw a Lewis structure. 2. Show the kinds of orbitals that overlap to form each bond. 3. Give approximate bond angles around each atom except hydrogen. (a) \([NH_2]^-\) (b) \([CH_2OH]^+\) (c) \(\mathrm{CH}_{2}=\mathrm{N}-\mathrm{CH}_{3}\) (d) \(CH_3-CH=CH_2\) (e) \(\mathrm{HC} \equiv \mathrm{C}-\mathrm{CHO}\) (f) \(H_2N-CH_2-CN\)

In most amines, the nitrogen atom is sp3 hybridized, with a pyramidal structure and bond angles close to 109. In urea, both nitrogen atoms are found to be planar, with bond angles close to 120. Explain this surprising finding. (Hint: Consider resonance forms and the overlap needed in them.) H2N C NH2 O urea

Predict the hybridization and geometry of the carbon and nitrogen atoms in the following molecules and ions. (Hint: Resonance.) (a) (a) CH3 C CH2 O (b) H2NCHCHC + H2 (c) C - H2 CN ((d) d) N ((e) e) N + (f) O N + H (g) O NH (h) O H N (i) O H

Draw orbital pictures of the pi bonding in the following compounds: (a) \(\mathrm{CH}_{3} \mathrm{COCH}_{3}\) (b) HCN (c) \(\mathrm{CH}_{2}=\mathrm{CH}-\mathrm{CHCHCN}\) (d) \(\mathrm{CH}_{3} \mathrm{C} \equiv \mathrm{CCHO}\) (e) \(\mathrm{CH}_{3} \mathrm{CH}=\mathrm{C}=\mathrm{CHCH}_{3}\) (f) \(\mathrm{CH}_{3}-\mathrm{CH}=\mathrm{N}-\mathrm{CH}=\mathrm{C}=\mathrm{O}\)

(a) Draw the structure of cis- CH3CHCHCH2CH3 showing the pi bond with its proper geometry. (b) Circle the six coplanar atoms in this compound. (c) Draw the trans isomer, and circle the coplanar atoms. Are there still six? (d) Circle the coplanar atoms in the following structure: CH3

In pent-2-yne \(\left(\mathrm{CH}_{3} \mathrm{CCCH}_{2} \mathrm{CH}_{3}\right)\), there are four atoms in a straight line. Use dashed lines and wedges to draw a three-dimensional representation of this molecule, and circle the four atoms that are in a straight line.

Which of the following compounds show cis-trans isomerism? Draw the cis and trans isomers of the ones that do. (a) \(\mathrm{CH}_{3} \mathrm{CH}=\mathrm{CHCH}_{3}\) (b) \(\mathrm{CH}_{3}-\mathrm{C} \equiv \mathrm{C}-\mathrm{CH}_{3}\) (c) \(\mathrm{CH}_{2}=\mathrm{C}\left(\mathrm{CH}_{3}\right)_{2}\) (d) cyclopentene, (e) (f) \(\mathrm{CH}_{3}-\mathrm{CH}=\mathrm{N}-\mathrm{CH}_{3}\)

Give the relationships between the following pairs of structures. The possible relationships are as follows: same compound, cis-trans isomers, constitutional (structural) isomers, and not isomers (different molecular formula). (a) CH3CH2CH2CH3 and (CH3)3CH (b) CH2CHCH2Cl and CHClCHCH3 (c) (c) CH3 CH3 CH3 CH3 and (d) CH3 CH3 and CH3 H3 C C CH2 (e) and CH3 CH3 (e) (f)(f) CH2 CH2 CH2CH3 CH3 and CH2 CH2 CH3 CH2CH3 (g) and (g) (h) and O O

Dimethyl sulfoxide (DMSO) has been used as an anti-inflammatory rub for race horses. DMSO and acetone appear to have similar structures, but the CO carbon atom in acetone is planar, while the SO sulfur atom in DMSO is pyramidal. Draw Lewis structures for DMSO and acetone, predict the hybridizations, and explain these observations. 3 SCH CH3 CH3 CH3 O C O DMSO acetone