Fall Workshop #1

Question #1
Split into two teams and play “Beat the Clock”. You’ll have 15 minutes to draw as many Lewis structures as you can. When your team is finished, show your work on the blackboard and discuss. Any unfinished structures can be completed thereafter.

C8H14NOBr
C9H10O2
C8H11NO
C4H8Cl-

If you have difficulty coming up with a Lewis structure, try following the steps below.

Step #1 / Using the molecular formula, determine the total number of electrons that can be used to make bonds and non-bonding electrons. For example, for C2H4O, there are 2 carbons (val. # = 4), 4 hydrogens (val. # = 1) and 1 oxygen (val. # = 6). So, (2x4)+(4x1)+(1x6) = 18 total electrons available to make bonds and non-bonding electrons. Remember that for + charges subtract 1 electron and for – charge add 1 electron.
Step #2 / Do the U calculation from class and determine the valence electron total
U = (2C + 2 + N – H – X)/2
Step #3 / Make single bond connections among the atoms using central atoms that can have multiple bonding partners – e.g. C, N, O (NOTE: there may be more than one way to do this --- ISOMERS) to come up with an INITIAL GUESS as to the Lewis structure (be sure to complete “octets”)
Step #4 / Check the formal charge on each atom and for the entire molecule -- if the charge does not agree, it may require you to rearrange atoms or to make additional (pi) bonds up or even a ring to satisfy the octet rule. Count electrons to make sure you have the same number you start with and end with and re-calculate formal charge.

Question #2
Further Analysis -- revisit your Lewis structures and do the following:

  1. Given the structures that you came up with, look inside the front cover of your text to determine which functional groups are present. (NOTE: if you cannot match with any, then your structure is likely not correct.)
  2. Convert each of your Lewis structures to line-bond (skeletal) structures
  3. Did any of you come up with two different structures for the same molecular formula? (These are called ISOMERS)

Question #3
Your workshop leader will draw sp3, sp2, and sphybridization models for carbon on the board. Take a few moments to reviewthe structures.Then, consider how these hybridized models arise from ground state electron configurations. You will likely want to show how electrons are configured first in the ground state and then how they are configured upon hybridization using an energy level diagram like we did in class.
(a) Be careful to use emptiest orbitals first for carbon and full orbitals first for oxygen.
(b) Evaluate each resulting hybridization state and propose what type of bonds (sigma/pi) each orbital will likely undergo upon incorporation of these hybdrizied atoms into organic molecules.
(c) Identify one functional group that contains each type of hybridized atom (see inside cover of your text).

* use the table below as a guide

hybridization state / atom / hybridized electron configuration (use energy level diagram) / # and types of bonds that will be formed/molecular geometry / type of functional group(s) this type of atom is present in (draw structure)
sp3 carbon / C
sp2 carbon / C
sp carbon / C
sp3 nitrogen / N
sp2 nitrogen / N
sp nitrogen / N
sp3 oxygen / O
sp2 oxygen / O

Question #4
If necessary, build models using your hand-held model kit for each of the molecules shown below.

  1. For each molecule, complete the structure by filling in any missing non-bonding electron pairs.
  2. Identify the hybridization state for all CARBON, OXYGEN, and NITROGEN atoms. (NOTE: halogens typically are not hybridized).
  3. Describe the molecular geometry around the atoms labeled A-L – use hand-held models if necessary to see the geometry.
  4. For each non-bonding electron pair on OXYGEN or NITROGEN, determine which orbital (p, sp, sp2, or sp3) it resides in.
  5. For each molecule, each person in the workshop should select 1 bond and take a turn describing the type of bond (sigma or pi) as well as the two orbitals (hybrid and/or atomic orbitals) that overlapped to make that bond. For example: C-H sigma bond = Csp3 + H1s

Question #5

For EACH of the following molecules, determine:

(a)Number of sp3 carbons, oxygens, and nitrogens

(b)Number of sp2 carbons, oxygens, and nitrogens

(c)Number of sp carbons, oxygens, and nitrogens

(d)Number of σ-bonds

(e)Number of π-bonds

(f)The degree of unsaturation