Determine whether each compound below exhibits a molecular dipole moment: (a) CH4 (b)

Determine the constitution of the compounds with the following molecular formulas: (a) CH4O (b) CH3Cl (c) C2H6 (d) CH5N (e) C2F6 (f) C2H5Br (g) C3H8

There are two constitutional isomers with molecular formula C3H7Cl, because there are two possibilities for the location of the chlorine atom. It can be connected either to the central carbon atom or to one of the other two (equivalent) carbon atoms. Draw both isomers.

Draw three constitutional isomers that have molecular formula C3H8O.

Draw all constitutional isomers that have molecular formula C4H10O.

Draw a Lewis dot structure for each of the following atoms: (a) Carbon (b) Oxygen (c) Fluorine (d) Hydrogen (e) Bromine (f) Sulfur (g) Chlorine (h) Iodine

Compare the Lewis dot structure of nitrogen and phosphorus and explain why you might expect these two atoms to exhibit similar bonding properties.

Name one element that you would expect to exhibit bonding properties similar to boron. Explain.

Draw a Lewis structure of a carbon atom that is missing one valence electron (and therefore bears a positive charge). Which second-row element does this carbon atom resemble in terms of the number of valence electrons?

Draw a Lewis structure of a carbon atom that has one extra valence electron (and therefore bears a negative charge). Which second-row element does this carbon atom resemble in terms of the number of valence electrons?

Draw a Lewis structure for each of the following compounds: (a) C2H6 (b) C2H4 (c) C2H2 (d) C3H8 (e) C3H6 (f) CH3OH

Borane (BH3) is very unstable and quite reactive. Draw a Lewis structure of borane and explain the source of the instability

There are four constitutional isomers with molecular formula C3H9N. Draw a Lewis structure for each isomer and determine the number of lone pairs on the nitrogen atom in each case.

Identify any formal charges in the structures below: (a) O H H H (b) H C N H H C H H H (c) H H H C O (d) H C H (e) H(f) H H C C H H O (g) Cl Al Cl Cl Cl Cl (h) C C H H H N H H O O (i)

Draw a structure for each of the following ions; in each case, indicate which atom possesses the formal charge: (a) BH4 - (b) NH2 - (c) C2H5 +

For each of the following compounds, identify any polar covalent bonds by drawing d+ and d- symbols in the appropriate locations: (a) H C H O H C H H C H H O C H H H (b) H C H F Cl (c) H C H Mg H Br (d) H O C H H C H H C O H H H O (e) H C C H H C H H H O (f) Cl C Cl

The regions of d+ in a compound are the regions most likely to be attacked by an anion, such as hydroxide (HO-). In the compound below, identify the two carbon atoms that are most likely to be attacked by a hydroxide ion: H C H H C H H C H H C O C H H Cl

Determine the electron configuration for each of the following atoms: (a) Carbon (b) Oxygen (c) Boron (d) Fluorine (e) Sodium (f) Aluminum

Determine the electron configuration for each of the following ions: (a) A carbon atom with a negative charge (c) A nitrogen atom with a positive charge (b) A carbon atom with a positive charge (d) An oxygen atom with a negative charge

Cyclopropane is a compound in which the carbon atoms form a three-membered ring: C H H CC H H H H Cyclopropane Each of the carbon atoms in cyclopropane is sp3 hybridized. Cyclopropane is more reactive than other cyclic compounds (four-membered rings, five-membered rings, etc.). Analyze the bond angles in cyclopropane and explain why cyclopropane is so reactive.

Consider the structure of formaldehyde: O Formaldehyde C H H (a) Identify the type of bonds that form the CPO double bond. (b) Identify the atomic orbitals that form each COH bond. (c) What type of atomic orbitals do the lone pairs occupy?

Sigma bonds experience free rotation at room temperature: C H H H H H H C In contrast, p bonds do not experience free rotation. Explain. (Hint: Compare Figures 1.24 and 1.29, focusing on the orbitals used in forming a s bond and the orbitals used in forming a p bond. In each case, what happens to the orbital overlap during bond rotation?)

Below are the structures of two common over-the-counter pain relievers. Determine the hybridization state of each carbon atom in these compounds: (a) C C C C C C H O C O C H H H O O H Acetylsalicyclic acid (aspirin) C H H H (b) O O C C C C C C C C H H C H H C C C H H H H H H H H H C H H H H H Ibuprofen (Advil or Motrin)

Determine the hybridization state of each carbon atom in the following compounds: (a) CC H H H H C C (b) O H H C C

Rank the indicated bonds in terms of increasing bond length: C C C H C H C C H H H C H H H H

Predict the geometry for the central atom in each of the compounds below: (a) NH3 (b) H3O+ (c) BH4 - (d) BCl3 (e) BCl4 - (f) CCl4 (g) CHCl3 (h) CH2Cl2

Predict the geometry for all atoms except hydrogen in the compounds below: (a) N O C C C C C C H H H H H H H H H H H O (b) O N N C C C C C C C H H H H H H H H H H H H (c) C C C C C C C C H H H H H H H H

Compare the structures of a carbocation and a carbanion: C Carbocation Carbanion In one of these ions, the central carbon atom is trigonal planar; in the other it is trigonal pyramidal. Assign the correct geometry to each ion.

Identify the hybridization state and geometry of each carbon atom in benzene. Use that information to determine the geometry of the entire molecule: Benzene C C C C C H C H H H H H

Identify whether each of the following compounds exhibits a molecular dipole moment. For compounds that do, indicate the direction of the net molecular dipole moment: (a) CHCl3 (b) CH3OCH3 (c) NH3 (d) CCl2Br2 (e) O C C H CC H H H H H H H (f) O C C O C C H H H H H H H H (g) O O C C C C C C H H H H H H H H (h) C C C C C C H H H H H H O O H H (i) Cl C C HH Cl (j) Cl Cl C C H H (k) Cl Cl C C H H (l) Cl Cl Cl Cl C

Which of the following compounds has the larger dipole moment? Explain your choice: CHCl3 or CBrCl3

Bonds between carbon and oxygen (C!O) are more polar than bonds between sulfur and oxygen (S!O). Nevertheless, sulfur dioxide (SO2) exhibits a dipole moment while carbon dioxide (CO2) does not. Explain this apparent anomaly.

For each of the following pairs of compounds, identify the higher boiling compound and justify your choice: (b) C C C C C C C C C C C H H H H H H H H H H H H H H H H H H H H H H (c) C C C H H H H H H H H H H C O H H H C C C H H H H H H H O C C C C H H H H H H H H H C O H C C C C H H H H H H H H H H O (d) C C C C H C C H H H H H H H H H H H H H H C H H C H H C C H H C H H H C H H H O O H

Arrange the following compounds in order of increasing boiling point: C C H H H H C H H C H H C H H H H C C C H H H H H H H H H C O H C C H H H C H H C H H C H H H H H H C O H C C C C H H H H H H H H H C H H H H H H H H C C C H C C H H H H H H

Draw structures for all constitutional isomers with the following molecular formulas: (a) C4H10 (b) C5H12 (c) C6H14 (d) C2H5Cl (e) C2H4Cl2 (f) C2H3Cl3

Draw structures for all constitutional isomers with the molecular formula C4H8 that have: (a) Only single bonds (b) One double bond

For each compound below, identify any polar covalent bonds and indicate the direction of the dipole moment using the symbols d+ and d-: (a) HBr (b) HCl (c) H2O (d) CH4O

For each pair of compounds below, identify the one that would be expected to have more ionic character. Explain your choice. (a) NaBr or HBr (b) BrCl or FCl

Draw a Lewis dot structure for each of the following compounds: (a) CH3CH2OH (b) CH3CN

Predict the geometry of each atom except hydrogen in the compounds below: (a) H C CC C H H H H H H H H @ (b) C C H H H H C H O H H ! (c) N C C O H H H H H H H H ! (d) C C C H H H H H H H O@

Draw a Lewis structure for a compound with molecular formula C4H11N in which three of the carbon atoms are bonded to the nitrogen atom. What is the geometry of the nitrogen atom in this compound? Does this compound exhibit a molecular dipole moment? If so, indicate the direction of the dipole moment.

Draw a Lewis structure of the anion AlBr4 - and determine its geometry.

Draw the structure for the only constitutional isomer of cyclopropane: Cyclopropane C H H CC H H H H

Determine whether each compound below exhibits a molecular dipole moment: (a) CH4 (b) NH3 (c) H2O (d) CO2 (e) CCl4 (f) CH2Br2

Identify the neutral element that corresponds with each of the following electron configurations: (a) 1s 2 2s 2 2p4 (b) 1s 2 2s 2 2p5 (c) 1s 2 2s 2 2p2 (d) 1s 2 2s 2 2p3 (e) 1s 2 2s 2 2p6 3s 2 3p5

In the compounds below, classify each bond as covalent, polar covalent, or ionic: (a) NaBr (b) NaOH (c) NaOCH3 (d) CH3OH (e) CH2O

Draw structures for all constitutional isomers with the following molecular formulas: (a) C2H6O (b) C2H6O2 (c) C2H4Br2

Draw structures for any five constitutional isomers with molecular formula C2H6O3.

For each type of bond below, determine the direction of the expected dipole moment: (a) C!O (b) C!Mg (c) C!N (d) C!Li (e) C!Cl (f) C!H (g) O!H (h) N!H

Predict the bond angles for all bonds in the following compounds: (a) CH3CH2OH (b) CH2O (c) C2H4 (d) C2H2 (e) CH3OCH3 (f) CH3NH2 (g) C3H8 (h) CH3CN

Identify the expected hybridization state and geometry for the central atom in each of the following compounds: (a) N H H H (b) B H H H (c) C H H H ! (d) C H H H @ (e) O H H

Count the total number of s bonds and p bonds in the compound below: H H H H C C C C H H H C C N H H O

For each pair of compounds below, predict which compound will have the higher boiling point and explain your choice: (a) CH3CH2CH2OCH3 or CH3CH2CH2CH2OH (b) CH3CH2CH2CH3 or CH3CH2CH2CH2CH3 (c) C C C H H H H H HO or H H C H H C H H H H

Which of the following pure compounds will exhibit hydrogen bonding? (a) CH3CH2OH (b) CH2O (c) C2H4 (d) C2H2 (e) CH3OCH3 (f) CH3NH2 (g) C3H8 (h) NH3

For each case below, identify the most likely value for x: (a) BHx (b) CHx (c) NHx (d) CH2Clx

Identify the hybridization state and geometry of each carbon atom in the following compounds: (a) C H H C C H H C C C (b) C C C O H C H H H H H H H (c) C H H CC H H H H

Ambien is a sedative used in the treatment of insomnia. It was discovered in 1982 and brought to market in 1992 (it takes a long time for new drugs to undergo the extensive testing required to receive approval from the Food and Drug Administration). Identify the hybridization state and geometry of each carbon atom in the structure of this compound: N O Zolpidem (Ambien) N C N C C C C C C C C C C C C C C CC C H H H H H H H H H HH HH H H H H H H H H

Identify the most electronegative element in each of the following compounds: (a) CH3OCH2CH2NH2 (b) CH2ClCH2F (c) CH3Li

Nicotine is an addictive substance found in tobacco. Identify the hybridization state and geometry of each of the nitrogen atoms in nicotine: N Nicotine C C C C C C C C C C H H H H H H H H H H H H H

Below is the structure of caffeine, but its lone pairs are not shown. Identify the location of all lone pairs in this compound: Caffeine N N C C N C C N O O C C H H H H H H H H H H

There are two different compounds with molecular formula C2H6O. One of these isomers has a much higher boiling point than the other. Explain why

Identify which compounds below possess a molecular dipole moment and indicate the direction of that dipole moment: (a) Cl Cl C C C C C H C H H H (b) Cl Cl C C C C C H C H H H (c) Cl Cl C C C C C H C H H H (d) Cl Br C C C C C H C H H H

Methylene chloride (CH2Cl2) has fewer chlorine atoms than chloroform (CHCl3). Nevertheless, methylene chloride has a larger molecular dipole moment than chloroform. Explain.

Consider the three compounds shown below and then answer the questions that follow: Compound A C H C H H H C H H C H H H N Compound B Compound C C C H H C H H C H H H N C H H H N H CC C H H H H H (a) Which two compounds are constitutional isomers? (b) Which compound contains a nitrogen atom with trigonal pyramidal geometry? (c) Identify the compound with the greatest number of s bonds. (d) Identify the compound with the fewest number of s bonds. (e) Which compound contains more than one p bond? (f) Which compound contains an sp2 -hybridized carbon atom? (g) Which compound contains only sp3 -hybridized atoms (in addition to hydrogen atoms)? (h) Which compound do you predict will have the highest boiling point? Explain.

Propose at least two different structures for a compound with six carbon atoms that exhibits the following features: (a) All six carbon atoms are sp2 hybridized. (b) Only one carbon atom is sp hybridized, and the remaining five carbon atoms are all sp3 hybridized (remember that your compound can have elements other than carbon and hydrogen). (c) There is a ring, and all of the carbon atoms are sp3 hybridized. (d) All six carbon atoms are sp hybridized, and the compound contains no hydrogen atoms (remember that a triple bond is linear and therefore cannot be incorporated into a ring of six carbon atoms).

Draw all constitutional isomers with molecular formula C5H10 that possess one p bond.

With current spectroscopic techniques (discussed in Chapters 1517), chemists are generally able to determine the structure of an unknown organic compound in just one day. These techniques have only been available for the last several decades. In the first half of the twentieth century, structure determination was a very slow and painful process in which the compound under investigation would be subjected to a variety of chemical reactions. The results of those reactions would provide chemists with clues about the structure of the compound. With enough clues, it was sometimes (but not always) possible to determine the structure. As an example, try to determine the structure of an unknown compound, using the following clues: The molecular formula is C4H10N2. There are no p bonds in the structure. The compound has no net dipole moment. The compound exhibits very strong hydrogen bonding. You should find that there are at least two constitutional isomers that are consistent with the information above. (Hint: Consider incorporating a ring in your structure.)

A compound with molecular formula C5H11N has no p bonds. Every carbon atom is connected to exactly two hydrogen atoms. Determine the structure of the compound.

Isonitriles (A) are an important class of compounds because of the versatile reactivity of the functional group, enabling the preparation of numerous new compounds and natural products. Isonitriles can be converted to isonitrile dihalides (B), which represents a useful procedure for temporarily hiding the reactivity of an isonitrile (Tetrahedron Lett. 2012, 53, 45364537). @! C N C N CCl C 2 B H3C H3C H3C H3C H3C H3C A (a) Identify the hybridization state for each highlighted atom in A. (b) One of the carbon atoms in A exhibits a lone pair. In what type of atomic orbital does this lone pair reside? (c) Predict the C!N!C bond angle in compound A. (d) Identify the hybridization state for each highlighted atom in B. (e) The nitrogen atom in B exhibits a lone pair. In what type of atomic orbital does this lone pair reside? (f) Predict the C!N!C bond angle in compound B.

In Section 1.12 we discussed the effect that branching can have on the boiling point of a compound. In certain instances, branching may also affect how a molecule can react with different molecules. We use the term steric hindrance to describe how branching can influence reactivity. For example, greater steric crowding may decrease the reactivity of a CRC p bond (Org. Lett. 1999, 1, 11231125). In the following molecule, identify each p bond and determine which has a greater degree of steric crowding. (Note: This is not the same as steric number.) C C C C C C C C C H H H H H H H H H H H H H H H H

Epichlorohydrin (1) is an epoxide used in the production of plastic, epoxy glues, and resins (reactions of epoxides will be discussed in Chapter 14). When epichlorohydrin is treated with phenol (2), two products are formed (3 and 4). At room temperature, these liquid products are difficult to separate from each other, but upon heating, these compounds are easily separated from one another. Explain these observations (Tetrahedron 2006, 62, 1096810979). C C O C Cl H H H H H C C HO C Cl H H H C C C C C C H H H H H OH NaOH, heat O C C C C C C H H H H H H H + C C O C O H H H H H C C C C C C H H H H H 1 2 3 4

Consider the following table that provides bond lengths for a variety of C!X bonds (measured in ). X = F X = Cl X = Br X = I C X 1.40 1.79 1.97 2.16 C X 1.34 1.88 2.10 C X 1.27 1.63 1.79 (a) Compare the data for bonds of the type Csp3!X. Describe the trend that you observe and offer an explanation for this trend. (b) Compare the data for bonds of the following types: Csp3!F, and Csp2!F, and Csp!F. Describe the trend that you observe and offer an explanation. (c) When comparing the bond lengths for Csp2!Cl and Csp!I, the trends established in the first two parts of this problem appear to be in conflict with each other. Describe how the two trends oppose each other, and then use the data in the table to determine which bond you predict to be longer. Explain your choice.

Positron emission tomography (PET) is a medical imaging tech nique that produces a threedimensional picture of functional processes in the body, such as the brain uptake of glucose. PET imaging requires the introduction of [18F]-fluorine (a radioactive isotope of fluorine) into molecules and can be achieved by several routes, such as the following (Tetrahedron Lett. 2003, 44, 91659167): + ! @ 18F 18F C C H H H H Br N C C H H H H O C C H H H H H H N C C H H H H O C C C H H C H H H H H H H H Br H H (a) Identify the hybridization for every heteroatom (atom other than C or H) in the three compounds. Note: Throughout this chapter, all lone pairs were drawn. We will soon see (Chapter 2) that lone pairs are often omitted from structural drawings, because they can be inferred by the presence or absence of formal charges. In this problem, none of the lone pairs have been drawn. (b) Predict the bond angle of each C!N!C bond in the product. (c) Identify the type of atomic orbital(s) that contain the lone pairs on the oxygen atom in the product.

Phenalamide A2 belongs to a class of natural products that are of interest because of their antibiotic, antifungal, and antiviral activity. In the first total synthesis of this compound, the following boronate ester was utilized (Org. Lett. 1999, 1, 17131715): O C O C C C C C B C O C C O H3C CH3 CH3 CH3 H H H H H H H H H (a) Determine the hybridization state of the boron atom. (b) Predict the O!B!O bond angle and then suggest a reason why the actual bond angle might deviate from the predicted value in this case. (c) The lone pairs have not been drawn. Draw all of them. (Hint: Note that the structure has no formal charges.)

The formation of a variety of compounds called oxazolidinones is important for the synthesis of many different natural products and other compounds that have potential use as future medicines. One method for preparing oxazolidinones involves the conversion of a hydroximoyl chloride, such as compound 1, into a nitrile oxide, such as compound 2 (J. Org. Chem. 2009, 74, 10991113): O C C C C C C C N H H H H H C N Cl C CC C C C OH H H H H H 1 2 (a) Identify any formal charges that are missing from the structures of 1 and 2. (b) Determine which compound is expected to be more soluble in a polar solvent, and justify your choice. (c) Determine the amount by which the C!C!N bond angle increases as a result of the conversion from 1 to 2.

The following compound belongs to a class of compounds, called estradiol derivatives, which show promise in the treatment of breast cancer (Tetrahedron Lett. 2001, 42, 85798582): C C C C C C C C C C C C C C C C C HO C O C C C C Cc Cb H Ca H H H H H H H H H H H H H H H H H H H H H H H H H H (a) Determine the hybridization state of Ca, Cb, and Cc. (b) Determine the H!Ca!Cb bond angle. (c) Determine the Ca!Cb!Cc bond angle. (d) Cb exhibits two p bonds: one to Ca, and the other to Cc. Draw a picture of Ca, Cb and Cc that shows the relative orientation of the two different p orbitals that Cb is utilizing to form its two p bonds. Also show the p orbitals on Ca and Cc that are being used by each of those atoms. Describe the relative orientation of the p orbitals on Ca and Cc.

The study of analogues of small peptide chains (Chapter 25), called peptidomimetics, provides models to understand the observed stabilizing effects in larger peptides, including enzymes (natures cata lysts). The following structure shows promise for studying how enzymes coil up into very discrete shapes that endow them with catalytic func tion (Org. Lett. 2001, 3, 38433846): O C O C N H3C H3C H3C C H H CH2 N C H3C CH3 H C H O N H C CH3 CH3 H (a) This compound has two N!C!N units, with differing bond angles. Predict the difference in bond angles between these two units and explain the source of the difference. (b) When this compound was prepared and investigated, it demon strated a preference for adopting a three-dimensional shape in which the two highlighted regions were in close proximity. Describe the inter action that occurs and create a drawing that illustrates this interaction.

Organic polymers (molecules with very high molecular weight) can be designed with pores (cavities) that are specifically tailored to fit a particular guest molecule due to complementary size, shape, and functional group interactions (intermolecular forces). Such systems are often inspired by binding sites in natural enzymes, which display a high degree of specificity for a particular guest. Several porous polymers were designed to bind bisphenol A (compound 1), a compound that is of environmental concern due to its ability to mimic natural hor mones such as estrogen (J. Am. Chem. Soc. 2009, 131, 88338838). Schematics of the binding sites of two of these polymers are shown below. Polymer A was found to have only limited selectivity in that it binds 1 or 2 (a control guest molecule) to a similar degree. Polymer B is more selective in that it binds strongly to 1 and weakly to 2. Draw pictures showing how each guest (1, 2) may bind in the pores of each polymer (A, B), and propose an explanation for the differences in bind ing specificity described above. C C C CH3 CH3 C C C CC CC C C C C CC N C C C C C N CC C CC C C C C C C C C CC C C C C C C C CC CC C C C HO OH H2N NH2 1 2 Binding site in polymer A Binding site in polymer B H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H