Organic Chem Chapter 3 Online HW

Consider a carbon atom that is sp hybridized. Indicate how many s, p, and sp orbitals exist on this carbon atom by sorting each orbital type. Consider the outer valence only.

0 s 2 p 2 sp Correct. When an atom is sp hybridized, it has two sp hybrid orbitals and two unhybridized p orbitals.

Below is the structure for the antibiotic mycomycin. How many sp3, sp2, and sp carbon atoms are there?

1 7 5

The structure below is called the neocarzinostatin core. For these questions, just consider the carbon framework, which is why the hydrogens are omitted. _________ sigma bonds _________ pi bonds

13 Part 1 is correct! The first bond between any two atoms is a σ bond and there are 13 σ bonds in this molecule. 6 Part 2 is correct! Double bonds contains a σ bond and π bond, and a triple bond contains a σ bond and two π bonds. This molecule contains two double bonds and two triple bonds, and therefore it has 6 π orbitals.

What is the percentage of p character in the hybrid orbitals on the carbon atoms in this structure? (2-methylpentane) __________ % p

75% Correct! All carbons are sp3 hybridized; therefore, each hybrid orbital is 25% s and 75% p.

Rank the following C-C sigma bonds (A, B, C, and D) in order of increasing bond strength.

Correct. As the hybridization of an atom goes from sp3 to sp2 to sp, its effective electronegativity increases and its sigma bonds become stronger.

Draw line structures for the cis and trans configurations of CH3CH2CH=CHCH3.

Correct. Because no rotation takes place about double bonds, some molecules containing a double bond can exist in either of two configurations. The substituents are on the same side in the cis configuration and on opposite sides in the trans configuration.

Based on what you have learned about nodes and orbitals, how many nodal planes are there in a 4p orbital? Choose one: Three Zero One Four Two

One Correct. Any p orbital will have one nodal plane separating its two lobes, regardless of its energy level.

How many molecular orbitals are generated from the linear combination of two sp2 orbitals? _________molecular orbitals will be generated

2 Correct! The number of atomic orbitals that are combined is equal to the number of molecular orbitals that are generated.

Which of the following orbitals is the best representation of an sp3 hybrid orbital? A (sphere) C (dumbbell with uneven sizes) E (sesame seed) B (dumbbell) D (four leaf clover)

C Correct! An sp3 orbital has two lobes, one much smaller than the other. Because of its relatively high percentage of p character, the lobes are more elongated than they are spherical.

What are the hybridization states (sp, sp2, sp3) for the C, N, and O atoms in the molecule CH2NOH?

C - sp2 N - sp2 O - sp3 Correct! The C and N atoms have electrons going in three directions and thus are sp2 hybridized. The O atom has electrons going in four directions and thus is sp3 hybridized.

Acetonitrile has the formula CH3CN. Match the correct hybridization and electron geometry for each nonhydrogen atom.

C(H3) - sp3, tetrahedral C(N) - sp, linear N - sp, linear Correct! The carbon of the CH3 group is sp3 hybridized. The carbon of the nitrile requires sp hybridization. This leaves two p orbitals to form π bonds to the adjacent nitrogen atom, which must also be sp hybridized.

Choose all of the molecules that can have BOTH cis and trans configurations.

Correct. A hypothetical 180° rotation about either group on the double bond results in two distinct structures.

Indicate how many of each type of molecular orbital exist in acetone. For each type of molecular orbital, enter an integer (0, 1, 2, etc.) with no decimal places. ________ bonding orbitals ________ antibonding orbitals ________ nonbonding orbitals

Part 1 10 Correct! There are 10 bonding orbitals. Part 2 10 Correct! There are 10 antibonding orbitals in acetone. Part 3 2 Correct! Each of the lone pairs on the oxygen is contained in a nonbonding molecular orbital.

How many bonding and antibonding molecular orbitals are there in methane, CH4? Part 1: __________ Bonding orbitals Part 2: __________ Antibonding orbitals

Part 1 4 Correct! Each C-H bond has a bonding molecular orbital, and there are four such bonds in methane. Part 2 4 Correct! Each C-H bond has an antibonding molecular orbital, and there are four such bonds in methane.

Part 1: Rank the following in order of increasing C-H bond length. Part 2: Select the molecule containing the strongest C-H bond. C2H6 C2H4 C2H2

Part 1 C2H2 < H2H4 < C2H6 Correct. When the hybridization of an atom has more s character, the effective electronegativity increases and the bonds become shorter and stronger. Part 2 C2H2 Correct. Carbons that are sp-hybridized have the most s character, so the bonds formed are shorter and stronger.

Consider molecular geometry and select all of the atoms that are in the same plane. Does this alkene have cis or trans configuration

Part 1 Correct. When two atoms are connected by a double bond, those atoms and any atoms to which they are directly bonded strongly prefer to lie in the same plane. Part 2 Correct. Substituents on alkenes with a trans configuration are on opposite sides of the double bond.

Below is the molecule acetonitrile. Part 1: Which hybrid orbitals make up the C-C σ bond? Choose one: sp3-sp3 sp2-sp sp3-sp sp3-sp2 Part 2: Which hybrid orbitals make up the C-N σ bond? Choose one: sp2-sp2 sp-sp sp-sp2 sp2-sp

Part 1 sp3-sp Correct! The CH3 carbon is sp3 hybridized and the nitrile carbon is sp hybridized. Part 2 sp-sp Correct! The nitrile carbon and nitrogen are sp hybridized.

Which of the following statements is the best explanation for the shapes of atomic orbitals? Choose one: Orbital shapes have no physical meaning, but we draw different shapes to distinguish orbitals from each other. The shape of an orbital describes a surface that encompasses about 90% of the probability of finding an electron around a nucleus. None of the other statements correctly explains why orbitals have the shapes they do. Orbital shapes describe the path traveled by an electron as it moves around the nucleus. The shape of an orbital encompasses all the possible locations of an electron around a nucleus.

The shape of an orbital describes a surface that encompasses about 90% of the probability of finding an electron around a nucleus Correct. The shapes of orbitals are generated by creating a surface that includes most of the probability of finding an electron around a nucleus.

How many linear combinations are possible when two p orbitals are combined? Choose one: Two None of these choices One Zero Four

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Select the HOMO and LUMO of ammonia. Part 1: HOMO Choose one: nonbonding MO N-H σ* N-H π s p N-H π* N-H σ Part 2: LUMO Choose one: N-H σ nonbonding MO N-H π s N-H π* N-H σ* p

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