(A)Menthol, used to flavor various foods and tobacco, is the most stable stereoisomer of 2-isopropyl-5-methylcyclohexanol. Draw its most stable conformation. Is the hydroxyl group cis or trans to the isopropyl group? To the methyl group? (b) Neomenthol is a stereoisomer of menthol. That is, it has the same constitution but differs in the arrangement of its atoms in space. Neomenthol is the second most stable stereoisomer of 2-isopropyl-5methylcyclohexanol; it is less stable than menthol but more stable than any other stereoisomer. Write the structure of neomenthol in its most stable conformation.

Why (a) is cis 3,4dimethylhex2ene? Why (b) is trans 6 Methylhept3ene?

Draw the most stable conformation of(a) trans-1-tert-butyl-3-(1,1-dimethylpropyl)cyclohexane.

Use a Newman projection about the indicated bond to draw the most stable conformer for each compound. (a) 3-methylpentane about the C2¬C3 bond

3,4-Dimethylpent-1-ene has the formula CH2“CH¬CH(CH3)¬CH(CH3)2. When pure (R)-3,4-dimethylpent-1-ene is treated with hydrogen over a platinum catalyst, the product is (S)-2,3-dimethylpentane. Has the chiral center retained its configuration during this hydrogenation, or has it been inverted?

4.(a). Draw the structures of (i) cis-1,4-Dibromocyclohexane and (ii) trans-1,4- Dibromocyclohexane. 4(b). Draw the most stable conformers of (i) cis-1,4-Dibromocyclohexane and (ii) trans-1,4-Dibromocyclohexane. 4(c)Which is more stable? (i) cis-1,4-Dibromocyclohexane or (ii) trans-1,4- Dibromolcyclohexane. Explain the reason for your choice.

Page of 11 ZOOM + A1. What is the arrangement of the bonds surrounding carbon in a saturated hydrocarbon? linear trigonal planar tetrahedral В trigonal bipyramidal A2. What is the definition of a constitutional isomer? A molecules with the same numbers and kinds of atoms arranged in different ways molecules with the same arrangements of atoms, but different arrangements of electrons molecules with the same connectivities, but different 3-D angles molecules with different isotopes of the same atoms В АЗ. How many hydrogen atoms does the following molecule contain? 12 В 16 18 Which functional group gives rise to a broad IR absorption between 3200 cm-1 and 3600 cm-1? A4. A O-H stretch C-H stretch O-H bend C-O stretch А5. How many resonances will appear in the 13C NMR spectrum of cyclopentanone? 3 4 Section A continues on the next page N468 ABCD ABCD ABCD

1 Provide the IUPAC name of the following compounds, with clear indication of stereochemistry for stereocenters and alkene. (a) (b) Br (c) Me. (d) Me

Given the structures of the following two tetramethylcyclohexanes: CH3 CH3 CH3 "CH3 CH3 CH3 A В (a) Draw the most stable chair conformation for both A and B. Which structure is lower in energy (most stable)? (b) Ring flip the above structures and draw the least stable chair conformation for both A and B. Which structure is highest in energy (least stable)?

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