Lipids

Question: Locate the isoprene units in biformene, a component of amber, and classify biformene as a monoterpene, sesquiterpene etc.

Question: Triacylglycerol L yields compound M when treated with excess ${\mathit{H}}_{\mathbf{2}}$, Pd-C. Ozonolysis of L ([1] ${\mathit{O}}_{\mathbf{3}}$ ; [2] ${\left(C{H}_3\right)}_{\mathbf{2}}$ affords compounds N-P. What is the structure of L?

Question: Locate the isoprene units in each compound.

Question: Classify each terpene and terpenoid in Problem 31.26 (e.g., as a monoterpene, sesquiterpene, etc.).

Crocin, which occurs naturally in crocus and gardenia flowers, is primarily responsible for the color of saffron. 

(a) What lipid and monosaccharides are formed by the hydrolysis of crocin? 

(b) Classify the lipid as a monoterpenoid, diperpenoid, etc., and locate the isoprene units.

Question: An isoprene unit can be thought of as having a head and a tail. The “head” of the isoprene unit is located at the end of the chain nearest the branch point, and the “tail” is located at the end of the carbon chain farthest from the branch point. Most isoprene units are connected together in a “head-to-tail” fashion, as illustrated. For both lycopene (Problem 31.26), and squalene (Figure 31.9), decide which isoprene units are connected in a head-to-tail fashion and which are not.

Question: Draw a stepwise mechanism for the conversion of neryl diphosphate to $\mathit{\alpha }\mathbf{-}\mathit{p}\mathit{i}\mathit{n}\mathit{e}\mathit{n}\mathit{e}$ , $\mathit{\alpha }\mathbf{-}\mathit{p}\mathit{i}\mathit{n}\mathit{e}\mathit{n}\mathit{e}$ is a component of pine oil and rosemary oil.

Question: The biosynthesis of lanosterol from squalene has intrigued chemists since its discovery. It is now possible, for example, to synthesize polycyclic compounds from acyclic or monocyclic precursors by reactions that form several C-C bonds in a single reaction mixture.

1. Draw a stepwise mechanism for the following reaction.
2. Show how X can be converted to 16, 17-dehydroprogesterone. (Hint: See Figure 24.5 for a related conversion.

Draw the products formed when triacylglycerol A is treated with each reagent. Rank compounds A, B and C in order of increasing melting point.

1. ${\mathbf{H}}_2\mathbf{O}$,${\mathbf{H}}^{\mathbf{+}}$
2. data-custom-editor="chemistry" ${\mathbf{H}}_{\mathbf{2}}$(excess),data-custom-editor="chemistry" $\mathbf{Pd}\mathbf{-}\mathbf{C}\to \mathbf{B}$
3.   ${\mathbf{H}}_{\mathbf{2}}$(1 equiv),  $\mathbf{Pd}\mathbf{-}\mathbf{C}\to \mathbf{C}$

Draw the products formed when triacylglycerol A is treated with each reagent. Rank compounds A, B and C in order of increasing melting point.

a. ${\mathbf{H}}_{\mathbf{2}}\mathbf{O}$ , ${\mathbf{H}}^{\mathbf{+}}$

b. ${\mathbf{H}}_{\mathbf{2}}$(excess), $\mathbf{Pd}\mathbf{.}\mathbf{C}\mathbf{\to }\mathbf{B}$

c. ${\mathbf{H}}_{\mathbf{2}}$(1 equiv), $\mathbf{Pd}\mathbf{.}\mathbf{C}\mathbf{\to }\mathbf{C}$

Locate the isoprene units in each compound.

a. 

b. 

c. 

d.  

Locate the isoprene units in each compound.

a. 

b.

c. 

d. 

Locate the isoprene units in biformene, a component of amber, and classify biformene as a monoterpene, sesquiterpene etc.

Draw the enantiomer and any two diastereomers of cholesterol. Does the OH group of cholesterol occupy an axial or equatorial position?

Treatment of cholesterol with mCPBA results in formation of a single epoxide A, with the stereochemistry drawn. Why isn’t the isomeric epoxide B formed to any extent?

One component of lanolin, the wax that coats sheep’s wool, is derived from cholesterol and stearic acid. Draw its structure, including the correct stereochemistry of all stereogenic centers.

Locate the isoprene units in each compound.

a.

b.

Convert the ball-and-stick model of androsterone to (a) a skeletal structure using wedges and dashed wedges around all stereogenic centers; and (b) a three-dimensional representation using chair cyclohexane rings.

Draw all possible constitutional isomers of a triacylglycerol formed from one mole each of palmitic, oleic, and linoleic acids. Locate the tetrahedral stereogenic centers in each constitutional isomer.

Draw the products formed when cholesterol is treated with each reagent. Indicate the stereochemistry around any stereogenic centers in the product.

1. ${\mathbf{CH}}_{\mathbf{3}}\mathbf{COCl}$
   
2. ${\mathbf{H}}_{\mathbf{2}}\mathbf{,}\mathbf{ }\mathbf{Pd}\mathbf{-}\mathbf{C}$
3. PCC
4. $\mathbf{oleic}\mathbf{ }\mathbf{acid}\mathbf{,}\mathbf{ }{\mathbf{H}}^{\mathbf{+}}$
5. $\left[1\right]{\mathbf{BH}}_{\mathbf{3}}\mathbf{·}\mathbf{THF}\mathbf{;}\left[2\right]{\mathbf{H}}_{\mathbf{2}}{\mathbf{O}}_{\mathbf{2}}\mathbf{,}\mathbf{-}\mathbf{OH}$
   

Draw a stepwise mechanism for the following conversion, which forms camphene. Camphene is a component of camphor and citronella oils.

Draw a stepwise mechanism for the following reaction.

Farnesyl diphosphate is cyclized to sesquiterpene A, which is then converted to the bicyclic product epi-aristolochene. Write a stepwise mechanism for both reactions.

A flask contains 1/3 mole of H₂ and 2/3 mole of He. Compare the force on the wall per impact of H2 relative to that for He.

Consider separate 1.0-L samples of O₂(g) and He(g), both at 25^oC and the same pressure. Compare the change in momentum per impact and the number of impacts per second in the two samples.