Alkenes: Structure and Reactivity

Calculate the degree of unsaturation in each of the following formulas:

1. Cholesterol ${\mathrm{C}}_{27}{\mathrm{H}}_{46}\mathrm{O}$,  
2. DDT ${\mathrm{C}}_{14}{\mathrm{H}}_9{\mathrm{Cl}}_5$, 
3. Prostaglandin E₁ , ${\mathrm{C}}_{20}{\mathrm{H}}_{34}{\mathrm{O}}_5$
4. Caffeine, ${\mathrm{C}}_8{\mathrm{H}}_{10}{\mathrm{N}}_4{\mathrm{O}}_2$
5. Cortisone ,${\mathrm{C}}_{21}{\mathrm{H}}_{28}{\mathrm{O}}_5$ 
6. Atropine, ${\mathrm{C}}_{17}{\mathrm{H}}_{23}{\mathrm{NO}}_3$

Draw structures corresponding to the following IUPAC names:

Change the following old names to new, post-names, and draw the structure of each compound:    

$\mathbf{\text{2,5,5-Trimethyl-2-hexene}}$.

Change the following old names to new, post-names, and draw the structure of each compound:    $\mathbf{\text{2,3-Dimethyl-1,3-cyclohexadiene}}$

The sex attractant of the common housefly is an alkene $cis-\mathbf{9}-\mathbf{tricosene}$ named. Draw its structure. (Tricosane is the straight-chain alkane ${\mathbf{C}}_{23}{\mathbf{H}}_{48}$ .)   

Which of the following compounds can exist as pairs of cis-trans isomers? Draw each cis-trans pair, and indicate the geometry of each isomer.${\text{CH}}_3{\text{CH =CH}}_2$

Which of the following compounds can exist as pairs of cis-trans isomers? Draw each cis-trans pair, and indicate the geometry of each isomer.${\left({\text{CH}}_3\right)}_2{\text{C =CHCH}}_3$

Which of the following compounds can exist as pairs of cis-trans isomers? Draw each cis-trans pair, and indicate the geometry of each isomer.${\text{CH}}_3{\text{CH}}_2{\text{CH =CHCH}}_3$

Which of the following compounds can exist as pairs of cis-trans isomers? Draw each cis-trans pair, and indicate the geometry of each isomer.${\left({\text{CH}}_3\right)}_2\text{C =C}\left({\text{CH}}_3\right){\text{CH}}_2{\text{CH}}_3$

Which of the following compounds can exist as pairs of cis-trans isomers? Draw each cis-trans pair, and indicate the geometry of each isomer.$\text{ClCH =CHCl}$

Which of the following compounds can exist as pairs of cis-trans isomers? Draw each cis-trans pair, and indicate the geometry of each isomer.$\text{BrCH =CHCl}$

Question: Name the following alkenes, including a cis or trans designation

Question: Name the following alkenes, including a cis or trans designation: 

Assign E or Z configuration to the following alkenes:

Assign E or Z configuration to the following alkenes:

Assign E or Z configuration to the following alkenes:

Assign stereochemistry (E or Z) to the double bond in the following compound, and convert the drawing into a skeletal structure (red = O):

Which member in each of the following sets ranks higher?

$-H \mathrm{or} -{\mathrm{CH}}_3$

Question: Which member in each of the following sets ranks higher?

$-\mathrm{Cl} \mathrm{or} -{\mathrm{CH}}_{2}Cl$

Which member in each of the following sets ranks higher?

 $-{\mathrm{CH}}_2{\mathrm{CH}}_2\mathrm{Br} \mathrm{or} -\mathrm{CH}={\mathrm{CH}}_2$

 Which member in each of the following sets ranks higher?

$-NHC{H}_3 or-OC{H}_3$

Which member in each of the following sets ranks higher?

$-{\mathrm{CH}}_2\mathrm{OHor}-\mathrm{CH}=\mathrm{O}$

Which member in each of the following sets ranks higher?

$-C{H}_{2}OC{H}_3 or -CH=\mathrm{O}$

Rank the substituents in each of the following sets according to the sequence rules:

$-{\mathrm{CH}}_3,-\mathrm{OH},-\mathrm{H},-\mathrm{Cl}$

Rank the substituents in each of the following sets according to the sequence rules:

$-{\mathrm{CH}}_3,-{\mathrm{CH}}_2{\mathrm{CH}}_3,-\mathrm{CH}={\mathrm{CH}}_2,{\mathrm{CH}}_2\mathrm{OH}$

Rank the substituents in each of the following sets according to the sequence rules:

$-{\mathrm{CO}}_2\mathrm{H},-{\mathrm{CH}}_2\mathrm{OH},-\mathrm{C}\equiv \mathrm{N},-{\mathrm{CH}}_2{\mathrm{NH}}_2$

Rank the substituents in each of the following sets according to the sequence rules:

$-C{H}_{2}C{H}_3,-\mathrm{C}\equiv CH,-\mathrm{C}\equiv \mathrm{N},-C{H}_{2}OC{H}_3$

Assign E or Z configuration to the following alkenes:

Name the following alkenes, and tell which compound in each pair is more stable:

Name the following alkenes, and tell which compound in each pair is more stable:

Name the following alkenes, and tell which compound in each pair is more stable:

Predict the products of the following reactions:

What alkenes would you start with to prepare the following products?

Show the structures of the carbocation intermediates you would expect in the following reactions:

Q 51 Normally, a trans alkene is more stable than its cis isomer trans-Cyclooctene, however, is less stable than cis-cyclooctene by 38.5 kJ/mol. Explain.

Fucoserratene and ectocarpene are sex pheromones produced by marine brown algae. What are their systematic names? (Ectocarpene is a bit difficult; make your best guess, and then check your answer in the Study Guide and Solutions Manual.)

The isobutyl cation spontaneously rearranges to the tert-butyl cation by a hydride shift. Is the rearrangement exergonic or endergonic? Draw what you think the transition state for the hydride shift might look like according to the Hammond postulate.

Reaction of 2,3-dimethyl-1-butene with HBr leads to an alkyl bromide, . On treatment of this alkyl bromide with KOH in methanol, elimination of HBr occurs and a hydrocarbon that is isomeric with the starting alkene is formed. What is the structure of this hydrocarbon, and how do you think it is formed from the alkyl bromide?

Calculate the degree of unsaturation in each of the following formulas:

b) DDT, ${\mathrm{C}}_{14}{\mathrm{H}}_9{\mathrm{Cl}}_5$

Draw a skeletal structure of the following carbocation. Identify it as primary, secondary, or tertiary, and identify the hydrogen atoms that have the proper orientation for hyperconjugation in the conformation shown.

What about the second step in the electrophilic addition of HCl to an alkene—the reaction of chloride ion with the carbocation intermediate? Is this step exergonic or endergonic? Does the transition state for this second step resemble the reactant (carbocation) or product (alkyl chloride)? Make a rough drawing of what the transition-state structure might look like.

On treatment with HBr, vinylcyclohexane undergoes addition and rearrangement to yield 1-bromo-1-ethylcyclohexane. Using curved arrows, propose a mechanism to account for this result.

Name the following alkenes, and convert each drawing into a skeletal structure:

The following alkyl bromide can be made by HBr addition to three different alkenes. Show their structures.

Predict the major product and show the complete mechanism for each electrophilic reaction below.

Name the following alkenes:

Draw structures corresponding to the following systematic names:

(a) (4E)-2, 4-Dimethyl-1, 4-hexadiene

(b) cis-3, 3-Dimethyl-4-propyl-1, 5-octadiene

(c) 4-Methyl-1, 2-pentadiene

(d) (3E, 5Z)-2, 6-Dimethyl-1, 3, 5,7-octatetraene

(e) 3-Butyl-2-heptene

(f) trans-2, 2, 5, 5-Tetramethyl-3-hexene

Name the following cycloalkenes:

Trans-Cyclooctene is less stable than cis-cyclooctene by 38.5 kJ/mol, but trans-cyclononene is less stable than cis-cyclononene by only 12.2 kJ/mol. Explain.

Aromatic compounds such as benzene react with alkyl chlorides in the presence of${\mathbf{AlCl}}_3$ catalyst to yield alkylbenzenes. This reaction occurs through a carbocation intermediate, formed by reaction of the alkyl chloride with${\mathbf{AlCl}}_3$.$\mathbf{\left(}\mathbf{R}\mathbf{-}\mathbf{Cl}\mathbf{+}{\mathbf{AlCl}}_3\mathbf{\to }{\mathbf{R}}^{+}\mathbf{+}{{\mathbf{AlCl}}_4}^{-}\mathbf{\right)}\frac{}{}$ How can you explain the observation that reaction of benzene with 1-chloropropane yields isopropylbenzene as the major product?