CHEM205 Worksheet - Nomenclature, Conformational Stability

Question # 00846092 Posted By: wildcraft Updated on: 09/21/2023 09:21 PM Due on: 09/22/2023
Subject Chemistry Topic General Chemistry Tutorials:
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CHEM 205 Worksheet (WS3) (58 points total)

Key Topics: Nomenclature, Conformational Stability, Newman Projections, Chair Structures

1. Using IUPAC rules (see Chapter 2.14-2.18 and Table 2.4 and 2.5 in text) provide a name to each structure below. Use common names for branched substituents were applicable. (6pts)

2. (a) Convert the semi-synthetic animal steroid shown below in bond-line form to its proper chair form by drawing in the missing non-hydrogen groups in their proper orientation and circle the groups that are axial. The skeleton is made up of the tetracyclic ring core. These 4 rings have been labeled A thru D for clarity. (7pts)

(b) Identify the two fused rings that represent a trans-decalin system (1pt) __________________

(c) Identify the two fused rings that do not represent a decalin skeleton. (1pt) ___________________

3. (a) Sighting down the C1 → C2 bond, consider the bond-line structure shown below. Using the

Newman projection templates provided, draw all three staggered conformations in Newman projection form in order of increasing stability about the C1 → C2 bond. (6pts) You may assume that iPr > Et > Cl in terms of size.

 (b) Sighting down the C3 → C4 bond, consider the bond-line structure shown below. Using the Newman projection templates provided, draw all three eclipsed conformations in Newman projection form in order of increasing stability about the C3 → C4 bond. (6pts)

(c) (i) Convert the chair structure below into its proper Newman projection using the template provided.

You need to fill in the empty boxes with the correct substituents (hydrogen and non-hydrogen groups).

Use the numbering scheme provided. (4pts)

(ii) Circle the bond-line structure below that best represents the same structure provided above in part c(i) (2pts).

(iii) (1pt) Is the iPr group at C-1 in the chair axial or equatorial? ___________________

(iv) (1pt) Is the CH3 group at C-2 in the chair axial or equatorial? ___________________

Me

H

H Pr

H H

H H

4. For (a) circle the most relative stable structure. Show work by drawing relevant chair structures and/or Newman projections (as needed) to clearly illustrate why. Explain your choice with a few words (no more than one sentence). It is best practice here that only the most stable conformations for each compound are being compared. For (b), provide a brief explanation for why chair 1 is more stable than chair 2. (10pts)

5. (a) (3pts) Provide a systematic (IUPAC) name for the structure below. You may ignore stereochemistry.

(b) Draw the structure of each compound below. Be sure to clearly show the relative stereochemistry.

Then, circle the compound that will have the highest heat of combustion. (4pts)

6. Draw and compare the Newman projections of when the OH groups are anti to each other versus when they are gauche to each other. Then, explain in a few words why the compound is more stable in the conformation where the OH groups are gauche to each other. (6pts)

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