2. Please consider the two all 'cis' isomers of trimethylcyclohexane drawn below. Draw the two chair conformers of each stereoisomer below (1 and 2) and calculate their torsional interaction energies in order to identify the lower energy conformer for each stereoisomer. Based on your calculations, state which of the two stereoisomers 1 and 2 is less stable and which is more stable. [1,3-diaxial CH3<--> CH3 = 3.7kcal/mol; 1,3-diaxial CH3 <--> H = 0.88kcal/mol; cis-1,2 (axial:equatorial) CH3 <-->CH3 = 0.88kcal/mol; trans-1,2-diequatorial CH3 <-->CH3 = 0.88kcal/mol) all-cis-1,2,3- 1 all-cis-1,2,4- 2

2. Please consider the two all 'cis' isomers of trimethylcyclohexane drawn below. Draw the two chair conformers of each stereoisomer below (1 and 2) and calculate their torsional interaction energies in order to identify the lower energy conformer for each stereoisomer. Based on your calculations, state which of the two stereoisomers 1 and 2 is less stable and which is more stable. [1,3-diaxial CH3<--> CH3 = 3.7kcal/mol; 1,3-diaxial CH3 <--> H = 0.88kcal/mol; cis-1,2 (axial:equatorial) CH3 <-->CH3 = 0.88kcal/mol; trans-1,2-diequatorial CH3 <-->CH3 = 0.88kcal/mol) all-cis-1,2,3- 1 all-cis-1,2,4- 2

Organic Chemistry

8th Edition

ISBN:9781305580350

Author:William H. Brown, Brent L. Iverson, Eric Anslyn, Christopher S. Foote

Publisher:William H. Brown, Brent L. Iverson, Eric Anslyn, Christopher S. Foote

Chapter2: Alkanes And Cycloalkanes

Section2.5: Conformations Of Alkanes And Cycloalkanes

Problem 2.9P: Following is a chair conformation of cyclohexane with the carbon atoms numbered 1 through 6. (a)...

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Following is a chair conformation of cyclohexane with the carbon atoms numbered 1 through 6. (a) Draw hydrogen atoms that are above the plane of the ring on carbons 1 and 2 and below the plane of the ring on carbon 4. (b) Which of these hydrogens are equatorial? Which are axial? (c) Draw the alternative chair conformation. Which hydrogens are equatorial? Which are axial? Which are above the plane of the ring? Which are below it?
Fill in the blanks: cis-1,3-Dimethylcyclohexane has two different chair conformations: one withboth methyl groups in __________ positions and one with both methyl groups in ____________ positions.
Consider the molecule 1-bromo-2-methylbutane. C3 and C4 should be drawn as Et as in theexample. This group is called an ethyl group and can be considered a sphere about twice the sizeof a methyl group. Draw the following Newman projections sighting down the C1C2 bond... a. The lowest potential energy conformation. b. The highest potential energy staggered conformation.
2. Draw the most stable conformer of the substituted cyclohexane shown below. OCH 3 HOW HO LOCH3 CH3 CH3 Extension: If the -OCH3 stereocentre was inverted (i.e. pointed in the opposite direction) would the resulting compound be more or less stable that the compound shown above? Explain your reasoning. Note this question is NOT asking whether the resulting conformer is more or less stable (it would be less, as the large -OCH3 group would be axial), but rather, the molecule overall. In the current molecule, the 'best case' conformer has 2/3 groups equatorial - the largest group and the smallest group. If the -OCH3 stereocentre was inverted, you could ring-flip to get a conformer that again has 2/3 groups equatorial, this time the largest 2. This would be more stable than the most stable conformer of the original molecule.
5. Please consider the Newman projection of tartaric acid drawn below as an eclipsed conformer (1). Please draw the most stable conformer and two intermediate energy conformers noting that staggered conformers are lower in energy than eclipsed forms even if the staggered conformers have gauche relationships between groups. [Draw the substituents H and OH on the front carbons and H, OH and CO₂H on the back carbons based on staggered forms. -CO₂H is larger than -OH.] OH COH ICOOH COOH COOH 1 2 COOH COOH 3 4 Staggered Staggered Staggered (most stable) Indicate the number of each conformer above (1, 2, 3 and 4) that corresponds to the relative energies below. Ref=0 Rotation 6. (60 points) a. Are compounds 1 and 2 below enantiomers, diastereomers or identical? OH OH HO HO LOH HO HO OH 2 OH OH b. Please complete the zig-zag conformation of the compound (3R,4S)-3,4-dichloro-2,5-dimethylhexane by writing the respective atoms in the boxes. 3.
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2. For the following structure: (1S, 2R, 4R)-2-chloro-1-isopropyl-4-methylcyclohexane a. draw both chair conformations for the molecule b. identify whether the more stable stereoisomer.
For 1,2-dichloroethane: a.Draw Newman projections for all eclipsed conformations formed by rotation from 0° to 360° about the carbon-carbon single bond. b.Which eclipsed conformation(s) has (have) the lowest energy? Which has (have) the highest energy? c.Which, if any, of these eclipsed conformations are related by reflection?
3. Draw Newman projection for the highest and lowest energy conformers of your assigned molecule. Provide a rationale to support your answer. In other words, why is the highest energy conformer so high in energy? Why is the lowest energy conformer low in energy? Molecule (2R,3S)-2-Bromo-3- Floro butane
2. H3CO H3CO HO 1. Consider the molecule shown below. [1] Draw the two chair conformations for the compound. [2] Identify which of the two chair conformations is more stable and explain why. H3CO Jonoto NH₂ How are the following molecules related? (exactly the same, completely different, constitutional isomers, enantiomers, or diastereomers). OH OH OCH3 HO“ OH H3CO H3CO is content is protected and may not be shared, uploaded of ributed OCH3 HO,,, OH O... "OCH3
Consider (1R,2S,3S,4S)-1,4-dibromo-2-(tert-butyl)-3-methylcyclohexane. Circle the location (axial or equatorial) for each substituent in this molecule’s most stable chair conformer.
(5) Draw the most stable chair conformation of the cyclohexane shown below. CH3 CI H3C Br OH CH3