Organic Chemistry: Alkenes and Isomerism

1. Examine the two groups attached to one carbon atom of the double bond, figure out which of the two has the higher priority. 2. Do the same at the other carbon atom. 3. Compare the group of high priority on one carbon atom with the group of high priority on the other carbon atom. If the two groups of high priority are on the same side, they are Z; if not, they are E.

Means 'together'; the two groups of higher priority are on the same side of the double bond.

Means 'opposite'; the two groups of higher priority are on opposite sides of the double bond.

<p>Trans isomers are generally more stable than cis isomers.</p> Signup and view all the answers

<p>The addition of hydrogen to an alkene, an exothermic reaction.</p> Signup and view all the answers

<p>The more substituted the carbon of the double bond is, the more stable the alkene is.</p> Signup and view all the answers

<p>Cycloalkenes with five carbon atoms or fewer must exist in the cis form.</p> Signup and view all the answers

<p>The most important means for synthesizing alkenes.</p> Signup and view all the answers

<p>Dehydrohalogenation of alkyl halides and dehydration of alcohols.</p> Signup and view all the answers

<p>Conditions that promote an E2 mechanism.</p> Signup and view all the answers

<ol> <li>Use 2° or 3° alkyl halide; 2. Use bulky base; 3. High concentration of strong, nonpolarizable base; 4. EtONa/EtOH and t-BuOK/t-BuOH - common bulky bases; 5. High temperature.</li> </ol> Signup and view all the answers

<p>Whenever an elimination happens and produces the more stable/more highly substituted alkene.</p> Signup and view all the answers

<p>The major product of the reaction will be the more highly substituted alkene.</p> Signup and view all the answers

<p>When the preferential formation of one product occurs because its free energy of activation is lower than another product.</p> Signup and view all the answers

<p>The major product of the reaction will be the less substituted alkene.</p> Signup and view all the answers

<p>When an elimination happens and produces the less substituted alkene.</p> Signup and view all the answers

<p>The five atoms have to be coplanar, or lie in the same plane.</p> Signup and view all the answers

<p>They have to be coplanar because the orbitals involved in the developing pi bond need to be overlapped properly.</p> Signup and view all the answers

<p>Anti coplanar transition state.</p> Signup and view all the answers

<p>Only available when anti coplanar is unavailable, occurs with rigid molecules that cannot achieve anti.</p> Signup and view all the answers

<p>Alcohols undergo this to form an alkene when heated with a strong acid.</p> Signup and view all the answers

<p>An elimination reaction favored at higher temperatures.</p> Signup and view all the answers

<p>They depend on the structure of the alcohol substrate.</p> Signup and view all the answers

<p>Primary alcohols are the most difficult to dehydrate.</p> Signup and view all the answers

<p>Secondary alcohols are a bit easier to dehydrate.</p> Signup and view all the answers

<p>Tertiary alcohols dehydrate very easily.</p> Signup and view all the answers

<p>3° &gt; 2° &gt; 1°.</p> Signup and view all the answers

<p>Some of them undergo rearrangements of their carbon skeleton during dehydration.</p> Signup and view all the answers

<p>An E1 reaction in which the substrate is a protonated alcohol.</p> Signup and view all the answers

<p>3° is most stable, methyl is least stable.</p> Signup and view all the answers

<p>The formation of the carbocation.</p> Signup and view all the answers

<p>They are really really endergonic.</p> Signup and view all the answers

<p>Delocalization of the charge - three alkyl groups are present to contribute to electron density by hyperconjugation.</p> Signup and view all the answers

<p>Because the primary carbocation required for dehydration by E1 is pretty unstable.</p> Signup and view all the answers

<p>E2 mechanism.</p> Signup and view all the answers

<p>When a methyl group migrates with its pair of electrons to stabilize a carbocation structure.</p> Signup and view all the answers

<p>Also known as a methyl shift.</p> Signup and view all the answers

<p>Formation of the more stable alkene is favored.</p> Signup and view all the answers

<p>Can lead to a more stable carbocation.</p> Signup and view all the answers

<p>Favorable if ring strain occurs; expansion can relieve the strain.</p> Signup and view all the answers

<p>WAYYYYYY more acidic hydrogen than those bonded to alkenes or alkanes.</p> Signup and view all the answers

<p>From vicinal dihalides.</p> Signup and view all the answers

<p>A compound with halogens on adjacent carbons.</p> Signup and view all the answers

<p>By the addition of bromine to an alkene; the vic-dibromide can then be put through a double dehydrohalogenation.</p> Signup and view all the answers

<p>A very strong base that can be used to cause both dehydrohalogenations needed to synthesize alkyne in one step.</p> Signup and view all the answers

<p>3 equivalents.</p> Signup and view all the answers

<p>Has 2 halogen atoms bonded to the same carbon.</p> Signup and view all the answers

<p>Dehydrohalogenation.</p> Signup and view all the answers

<p>Using PCl5 to convert the ketone to gem-dichlorides, then synthesize alkynes.</p> Signup and view all the answers

<p>You can use a very strong base like sodium amide (NaNH2) to break it off and form an alkynide anion.</p> Signup and view all the answers

<p>They are good nucleophiles to perform C-C bond-forming reactions with 1° alkyl halides or 1° substrates.</p> Signup and view all the answers

<ol> <li>Preparation of alkynide ion requires Bronsted-Lowry acid/base chemistry; 2. Alkynide ion = Lewis base and acts as a nucleophile; 3. Alkyl halide = electrophile.</li> </ol> Signup and view all the answers

<p>Alkenes react with H in the presence of metal catalysts to add an H to each C of the double bond.</p> Signup and view all the answers

<p>When hydrogenation reactions occur with insoluble Pt, palladium, or nickel catalysts.</p> Signup and view all the answers

<p>When soluble catalysts to the mixture are involved in hydrogenation reactions.</p> Signup and view all the answers

<p>Addition reactions.</p> Signup and view all the answers

<p>Compounds with only C-C single bonds, containing the maximum number of hydrogen atoms possible.</p> Signup and view all the answers

<p>Compounds with C-C multiple bonds like alkenes and alkynes; they contain fewer than the maximum number of hydrogens.</p> Signup and view all the answers

<p>Reduced by catalytic hydrogenation.</p> Signup and view all the answers

<p>There is a high free energy of activation, and a catalyst is needed to lower it so it can take place at room temperature.</p> Signup and view all the answers

<p>Syn addition.</p> Signup and view all the answers

<p>When an addition occurs that puts the parts of the adding reagent on the same side/face of the reactant.</p> Signup and view all the answers

<p>When an addition occurs that puts the parts of the adding reagent on opposite sides/faces of the reactant.</p> Signup and view all the answers

<p>H2, Pd/CaCO3; metallic palladium deposited on calcium carbonate.</p> Signup and view all the answers

<p>Making cis-alkenes from disubstituted alkynes.</p> Signup and view all the answers

<p>When the alkyne is treated with lithium or sodium metal in ammonia or ethylamine at low temperatures.</p> Signup and view all the answers

<p>Anti addition of hydrogen to the triple bond of alkynes occurs when treated with Li or Na metal in ammonia or ethylamine at low temperatures.</p> Signup and view all the answers

<p>It produces an E or trans-alkene.</p> Signup and view all the answers

<ol> <li>Reactions that convert one functional group to another; 2. Reactions that make new C-C bonds.</li> </ol> Signup and view all the answers