Alkenes drawing

The following alkyl halide can be prepared by addition of HBr to two different alkenes. Draw the structures of both (reddish brown = Br). 

Step 2 of the iodination of benzene shows water acting as a base and removing a proton from the sigma complex. We did not consider the possibility of water acting as a nucleophile and attacking the carbocation, as in an electrophilic addition to an alkene. Draw the reaction that would occur if water reacted as a nucleophile and added to the carbocation. Explain why this type of addition is rarely observed. 

The following structure represents the carbocation intermediate formed in the addition reaction of HCl to an alkene. Draw the structure of the alkene (gray = C, ivory = H). 

For each of the following alkenes, draw structural formulas of all chloroalkanes that undergo dehydro-halogenation when treated with KOH to give that alkene as the major product (for some parts, only one chloroalkane gives the desired alkene as the major product for other parts, two chloroalkanes may work) ... 

Suggest a reason why treating 2-bromo-bicyclo[2.1.1]hexane (draw it) with KOH and ethanol leads to the less substituted alkene rather than the more substituted alkene (draw both alkenes)—despite the fact that these are E2 conditions. This observation led to what is known as Bredt s rule for reactions that produce an alkene unit in small bicyclic molecules. 

When the product from the reaction described in the preceding question is heated with acid, the product is commonly an alkene. Draw this alkene product and suggest a mechanism for its formation. 

The sex pheromone of the common housefly is cis-9-tricosene, where tricosene is the lUPAC name of a 23-carbon alkene. Draw the condensed formula of this molecule, marketed under the name Muscalure. 

For each of the following alkenes, draw the structure of two different alkyl halides that yield the given alkene as the only product of dehydrohalogenation. 

For each alkene draw all the likely products of electrophilic addition of one equivalent of strong acid, HX (where X = Cl, Br or I), and use curved arrows to show the mechanism of each reaction. (Some of the reactants are likely to undergo a carbocation rearrangement.)... 

Draw the other stereoisomer that might have been obtained from syn addition of hydrogen to each alkene. Is the observed product for each addition also the thermodynamic product Compare energies for alkene A+ H2 observed and not observed and alkene B+H2 observed and not observed. What structural factors seem to be responsible for the relative stabilities of the two products of each hydrogenation reaction ... 

Thomson NOW Click Organic Interactive to use a web-based palette to draw alkene structures based on their IUPAC names. 

When solving a problem that asks how to prepare a given product, always work backward. Look at the product, identify the functional group(s) it contains, and ask yourself, "How can I prepare that functional group " In the present instance, the product is a tertiary alkyl chloride, which can be prepared by reaction of an alkene with HC1. The carbon atom bearing the —Cl atom in the product must be one of the doublebond carbons in the reactant. Draw and evaluate all possibilities. 

Problem 6.18 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 endergontc 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. 

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

Draw the structures of alkenes that would yield the following alcohols on hydration (red - O). Tell in each case whether you would use hydroboration/ oxidation or oxymercuration. 

The following alkene undergoes hydroboration/oxidntion to yield a single product rather than a mixture. Explain the result, and draw the product showing its stereochemistry. 

Draw the structure of an alkene that yields only acetone, (CH3)2C = 0, on ozonolysis followed by treatment with Zn. 

Draw the alkene reactant, and identify the allylic positions. In this case, there are two different allylic positions we ll label them A and B. Now abstract an allylic hydrogen... 

Draw (lSP2S)-l,2-clibromo-l,2-diphenylethane so that you can see its stereochemistry and so that the —H and —Br groups Lo be eliminated are anti periplanar. Then carry out the elimination while keeping ail substituents in approximately their same positions, and see what alkene results. 

What stereochemistry do you expect for the alkene obtained by E2 elimination of, (lR /O-LZ-dibromo-l -diphenylethane Draw a Newman projection of the reacting conformation. 

The double bond of an enamine (alkene + amine) is much more nucleophilic than a typical alkene double bond. Assuming that the nitrogen atom in an enamine is. -hybridized, draw an orbital picture of an enamine, and explain why the double bond is electron-rich. 

You knowr the mechanism of HBr addition to alkenes, and you know the effects of various substituent groups on aromatic substitution. Use this knowledge to predict which of the following two alkenes reacts faster with HBr. Explain your answer by drawing resonance structures of the carbocation intermediates. 

Name the following amine, including R,S stereochemistry, and draw the product of its reaction with excess iodomethane followed by heating with Ag20 (Hofmann elimination). Is the stereochemistry of the alkene product Z or E Explain. 

Draw Lewis structures of the following molecules and identify each as an alkane, alkene, or alkyne (a) CH3CCCH3 ... 

So, we expect this reaction to be stereospecific, rather than stereoselective. That is, we expect only one alkene, rather than a mixture of stereoisomeric alkenes. In order to determine which alkene is obtained, we begin by drawing the Newman projection ... 

EXERCISE 11.1 Draw the product that you would expect from an anti-Markovnikov addition of H and Br across the following alkene ... 

We know which two groups are adding to the double bond, and we know the regiochemistry of the addition. But in order to draw the products correctly, we also need to know the stereochemistry of the reaction. To better explain this, we will redraw the alkene in a different way. 

This is an unusual way to draw an aUcene (where all bonds are shown as wedges and dashes, rather than straight lines), but this way of drawing the alkene will make it easier to explore stereochemistry. 

The examples we have seen so far have been acyclic alkenes (not containing a ring). When we add across cyclic alkenes, the products are easier to draw because we don t have to rotate and redraw the alkene before starting. Let s see an... 

---