CHEM 243 - Organic Chemistry I – Fall 2020

Worksheet #3: Watch videos in this order: 3-1, 3-2, 3-4. Video 3-3 will be covered on Worksheet #4. We will cover

videos 3-5 and 3-6 in the spring semester.

Target date for completion is Thursday, September 24 (or earlier!). Complete the following worksheet by the target

date by (1) working with a group of students during class time, and (2) working on your own outside of class. You can use

any resource available to you, but I strongly discourage the use of Wikipedia and online homework sites (like Chegg).

During class time you will get help from the course instructor, the Peer Leaders, and other students.

The purpose of this worksheet is to apply the principles you learned in the corresponding lecture videos. I will NOT

collect this worksheet. I advise you to print this worksheet and answer the questions in the space provided. I encourage

you to save this worksheet in your course notebook for study purposes, and I will post an answer key.

FORMAL QUIZ-1. Formal Quiz-1 will be given during your normal class time on Thursday, September 24 (TR class) or

Friday, September 25 (MWF class). The Quiz will count 100 points. Here are the logistics:

• Quiz-1 will cover material on Worksheets 1, 2 and 3. For Worksheet #3 you are only responsible for videos 3-1,

3-2 & 3-4. Video 3-3 will be included on Worksheet #4. We will cover videos 3-5 and 3-6 in the spring semester.

• You must attend your Zoom class meeting to take the Quiz and remain logged into the Zoom class. You do not

need to turn your camera on. This way if you have any questions I will be right there. I will place the link to the

Quiz in the chat box 10 minutes before class begins (you can start the quiz 10 minutes early).

• This Quiz will be timed! You should study and prepare for this Quiz as you might a regular in-class exam. You

will NOT have enough time to search the internet for answers!

• Quiz-1 will be designed to be completed in 40 minutes. After 40 minutes I will make an announcement that “time

is up”, and you will then have 10 minutes to finish up and email your Quiz to me (50 minutes total). After the 10-

minute warning, there will be a 2-point penalty for each minute received late.

• You must work alone on this Quiz. Working together will result in a ZERO score.

• You may use your class notes, and all information on the class web page. You may not search the internet for

answers (i.e., Google), and I monitor homework sites like Chegg. If I have evidence that you searched the

internet, you will receive a ZERO score.

• You will download the quiz through a link in the chat box as an MS Word document. I am assuming that you can

work with MS Word documents on your computer.

• After downloading, you will complete the Quiz electronically in MS Word. You will type your answers in text

boxes.

• When you are finished be sure to save the completed Quiz to your computer. I would appreciate it if you add your

LAST NAME to the document file name. Attach your completed quiz to an email and send to me

(ebrush@bridgew.edu). To verify that I received your email, before clicking “Send”, click the “Options” menu,

then make sure to check “Request a Delivery Receipt”.

• As discussed earlier and stated in the course Syllabus, I will not return your graded work, but I will post an

answer key, and you will be able to see your grades in Blackboard.

This work is based on Videos 3-1, 3-2 and 3-4. There are also a few REVIEW QUESTIONS included. PLEASE

NOTE: The ANSWER KEY to this worksheet will be posted Tuesday at 12:00 noon.

(1) Acids and Bases. For each acid draw its conjugate base, and for each base draw its conjugate acid. Be sure to label

atoms with their appropriate formal charge!

(c) HSO4- conjugate acid:

(base)

(2) Acids, Bases, Conjugate Acids, Conjugate Bases, and pKa’s. What follows is a series of acid-base reactions.

Although I expect that you should be able to identify the more common acids and bases, in some cases I have placed lone

pairs on the base. For each acid/base reaction shown below do the following:

(i) Label the Acid (A) and Base (B) reactants;

(ii) Label the Conjugate Acid (CA) and Conjugate Base (CB) products;

(iii) Using the pKa table, label each Acid (A) and Conjugate Acid (CA) with their corresponding pKa’s.

EXAMPLE:

(3) Periodic Table Trends and Acid Strength.

(a) As you go left-to-right across a row of the periodic table, does acid strength Increase or Decrease? (circle)

(b) As you go top-to-bottom down a column of the periodic table, does acid strength Increase or Decrease? (circle)

(c) Rank the four molecules below in order of increasing acidity (1 = weakest.......4 = strongest).

_______ _______ _______ _______

(d) Rank the following molecules in order of increasing acidity (1 = weakest.......4 = strongest).

HF H2O NH3 CH4

_______ _______ _______ _______

(e) Rank the following molecules in order of increasing acidity (1 = weakest.......4 = strongest).

H2Se H2Te H2O H2S

_______ _______ _______ _______

(4) Inductive Effects and Acid Strength.

(a) Briefly explain how Inductive Effects can affect the strength of acids.

(b) As the strength of a series of acids deceases, will their pKa values increase or decrease? (circle your answer)

(c) As the distance of an electronegative halogen atom from an acid proton increases, the acid pKa also increases. Is this

statement TRUE or FALSE? (circle your answer)

(d) The strength of three organic acids is being compared. Acid (A) has two Br atoms, acid (B) has one Br atom, and acid

(C) does not have any halogen atoms. Which is the strongest acid? ANSWER___________

(e) Match the following pKa values to the acids drawn below: 4.86 3.98 1.48 2.83

__________ __________ __________ __________

REVIEW QUESTIONS

(1) For the compound drawn at the right,

indicate the number of:

(a) 1o carbons _____ 2o carbons _____ 3o carbons _____ pi bonds _____

(b) What is the Hydrogen Deficiency? _____

(c) Indicate the Hybridization and Geometry for the atoms labeled A-D:

A ____________________ B ____________________ C ____________________ D ____________________

(c) Based on the functional groups present, which of the following IR bands might be present (circle):

1700 2100 3300 3200-3600

(2) Two unknown chemicals were analyzed and each found to have a molecular formula of C9H18O. Are the following

statements about these compounds TRUE or FALSE.

They must be constitutional isomers_____ Each unknown contains a double bond or a ring_____

They may be constitutional isomers or identical_____ The unknowns may be an alcohol, ether, aldehyde or ketone____

The Hydrogen Deficiency is 4_____ If a ring is present, all atoms must be sp3_____

(3) Zig-zag Structures. For each structure drawn below:

(i) Circle the “parent chain” (longest continuous carbon chain).

(ii) Indicate the number of carbons in your parent chain.

(ii) Based on the parent chain, draw an accurate zig-zag structure.

EXAMPLE:

# Carbons in parent chain: _______

Hint: The C’s in the ring are NOT part of the parent chain!

# Carbons in parent chain: _______

(4) Comparing Organic Structures. How are the following pairs of compounds related:

Identical or Different or Constitutional Isomers?

(5) Structure Identification and IR. An unknown organic compound has a formula of C4H8O

(a) Calculate the Hydrogen Deficiency for this unknown: ___________

(b) Based on the HD and Formula, what type(s) of functional groups might be present? CIRCLE all possibilities from the

list below:

alkene carbonyl alkyne alcohol (R-OH) ether (R-O-R) cycloalkyl

(c) The IR spectrum for this unknown is given below. What does the IR spectrum suggest about this unknown?

Answer:

(d) In addition to all the data given in parts a, b

and c, the unknown also has two 2o carbons and

one 1o carbon. In the space to the right, draw

one structure for this unknown consistent with

all the data given to you.

(6) Calculations. These calculations are based on the compound above: C4H8O

(a) What is the molecular mass of this molecule (4 significant figures): _________________________

(b) If you had 0.5034 grams of this compound, how many moles would you have? _____________________

(you do not need to show your work)

4000 3000 2000 1500 1000 500

wavenumber cm-1