Name _______________________________ Chem 221-01, Fall, 2020
Written Assignment #2
This assignment is worth a possible total of 100 points. Place your answer in the space provided. Remember that in the problems you must show ALL your work in writing in order to receive full credit for the answers in Part III. Read the “Guidelines” [course syllabus] for further information on what is needed to show your work.
No late papers are accepted except by previous arrangement with the instructor.
This assignment is due on Sunday, October 18, 2020 at 11:59PM electronically via Moodle.
PART I – True/False – Circle your response. ( 3 pts each , 12 pts total)
1. A carbon atom is called secondary (2o) if it is attached to two other carbon atoms.
True / False
2. In the name of an alkane with multiple substituents, you organize the names of the substituents in increasing number on the carbon chain (smallest number first, from left to right in the name). True / False
3. In studying the energy difference between the axial and equatorial positions for substituents on cyclohexane, we can generally say that the larger the substituent (such as butyl compared to methyl), the greater the energy difference. True / False
4. The terms “anti” and “gauche” refer to different arrangements in the “eclipsed” conformation. True / False
PAR T II – Multiple Choice – Circle your response. ( 9 pts each, 18 pts total)
Note that some questions may require more than one choice to be a complete response.
1. Circle all the true statements about the following two compounds
(CH3)3 C – C(CH3)3 and CH3CH2C(CH3)2CH2CH2CH3
(a) Both have the chemical formula C8H18.
(b) There are at least two secondary carbons in both structures.
(c) These two compounds have very similar boiling point values.
(d) The compound on the left has more branch points than the compound on the
2. The following two compounds have the structures shown by the ball-and-stick
models (See Section 3-11).
Circle all the true statements about these two structures.
(a) These two compounds can be said to be stereoisomers (Hint: See Section 1-19].
(b) These two compounds can be called geometric isomers.
(c) Both compounds have the same chemical formula, C7H14.
(d) Cycloheptane has the same chemical formula as in (c), and it would be called a
structural isomer with these two compounds, but not a stereoisomer with them.
PART III – Written Response (50 pts total)
This section requires that you SHOW YOUR WORK clearly and legibly in order to be eligible for full credit for each question. Otherwise, you will not receive full credit, even though you have the correct answer, numerically speaking!!!!! [See the “Guidelines” in the course syllabus.]
1. ( 14 pts ) The following names represent real compounds, but they are named incorrectly, not following IUPAC rules. Draw each structure from the name given, and then rename it according to the IUPAC rules.
Remember two important rules are that you need to use the longest continuous chain of carbons to name to compound, and you must number the carbons so that you have the lower numbers (closer to the first branch), as shown here in this example:
(a) 2,2-Dimethyl-6-ethyl-heptane __________________________________________
(b) 4-Ethyl-5,5-dimethylpentane __________________________________________
2. (12 pts) There are various ways to consider the structure and bond rotation of carbon compounds. Newman projections show a condensed version of the way a carbon-carbon bond can rotate, and also shows how the attached groups (such as -CH3) would be oriented.
(a) Give the name and chemical formula of the compound shown in these Newman projections.
Name:___________________ Chemical formula:_____________________
(b) Label each of the two Newman projections with its proper term, “eclipsed” or “staggered”
(c) Which of the two conformations has the higher energy? Explain why, and compare it to the other conformation.
(d) Two other terms for conformations are “anti” and “gauche”. briefly explain what these mean, and whether either applies to the images in this question.
3. (12 pts) Study the melting and boiling point trends in the alkanes (Figures 3-3 and 3-4, text).
For each pair below, identify which compound has the higher boiling point, and explain why in terms of surface area and intermolecular forces. Draw the structural formula (See section 3-3) for both compounds in each pair.
(a) octane vs. 2,2,3-trimethylpentane Higher BP: _____________________
(b) nonane or 2-methylheptane Higher BP ______________________
4. (12 pts) While a cyclohexane ring cannot rotate fully around the C-C bonds, it can change conformation of the tetrahedral carbons, and “flip”.
(a) Label the following two molecules of cyclohexane as either “chair” or “boat” configuration. Note: In these models, the gold carbon atoms are higher than the blue carbons!
(b) Here is a relative energy diagram of cyclohexane as it moves from one conformation to another.
Briefly explain why (in terms of the atom arrangements) we see that conformation A has lower energy than conformation C, and identify them as either “chair” or “boat”.
A ______________ C _________________
PART IV – Technical Communication Response (20 pts)
These questions are intended as a scientific approach to the evaluation of a current issue in our technology and consumer use. This response will be focused on the chemistry of the issue, but cannot (and should not) be separated from other dimensions of the issue, such as social, health, or economic aspects.
Answer the following questions using the information provided in these articles. You must have legible, complete sentences in order to get full credit for a response, unless it is otherwise explicitly indicated.
Read the article “How we know disinfectants should kill the COVID-19 coronavirus” [C&EN, March 23, 2020, p. 7].
1.) Specific studies have considered how long the virus remains active on different types of surfaces. Describe some of the results obtained so far on hard surfaces or plastics.
( 2 – 3 sentences)
2.) The virus depends upon a protective coating to remain active. What is the nature of that coating, and why do alcohol products work so well? What is the difference between the effect of alcohol and of bleach on the virus? ( 3 – 4 sentences)
3.) What is the present situation with regard to the effectiveness of disinfectants, according to the EPA’s position? Explain, briefly, where we are in our understanding.
( 3 – 5 sentences)