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122 Cards in this Set
- Front
- Back
What reaction does this picture show? |
SN2 |
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A group that is lost during nucleophilic substitution or elimination. Typically a halide. The less basic, the better |
Leaving group |
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Rate of SN2 reaction |
Bimolecular, second order. Rate = k[reactant][nucleophile] |
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What happens during a SN2 reaction? |
Inversion of stereochemistry at site of backside attack, nucleophile attacks from opposite side of leaving group. |
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What type of reactant works best in the SN2 reaction? |
Methyl and primary carbons, because of steric hindrence. |
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Measure of a Lewis base to perform a substitution. |
Nucleophilicity More basic = more nucleophilic for the same atom. The smaller the atom the better because of steric effects. |
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What type of solvants are used in a SN2 reaction? |
Polar aprotic solvents: polar enough to dissolve the substrate and nucleophile but do not participate in hydrogen bonding with the nucleophile. Sometimes a salt. No H bonding in an aprotic solvant, but Hs can be present. |
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What type of solvant is used in an SN1 reaction? |
Polar protic, something with an H |
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What is created in an SN1 reaction? |
A racemic mixture, but more of the product with the opposite stereochemistry |
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What reactant preserves stereochemistry? |
OTs |
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What reactant inverts stereochemistry? |
SOCl |
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What kind of reaction happens with a hydrogen halide and alcohol? |
Substitution |
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What kind of reactants are used in an SN1 reaction? |
Tertiary and secondary carbons |
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Why are sulfonates good surrogates for alkyl halides? |
Sulfonates don't need to protonate, OH is therefore a worse leaving group than sulfonic acid, making sulfonate have an advantage in substitution reactions. |
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Is there rearrangement in E1 reactions? |
Yes |
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Are there rearrangements in E2 reactions? |
No, no carbocation formed |
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What happens in an E1 reaction? |
Alkenes are formed, sp2 hybridized carbons. Alkenes have shorter bond lengths than sp3 carbons. No stereoisomers. Works best with 2° and 3° carbons |
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What solvents are used in an E1 reaction? |
Strong acids, heat R-OH and H2SO4 |
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What is the nomenclature for an alkene with higher ranked groups on the same side? |
Z |
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What is the nomenclature for an alkene with higher ranked groups on opposite sides? |
E |
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What happens during an E2 reaction? |
Dehydrohalogenation of alkyl halides An alkyl halide becomes an alkene |
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What are the starting materials and solvants used in an E2 reaction? |
Alkyl halides carried out in a strong base. Works best with 2° and 3° carbons. Can work with 1° if (CH3)3OK is used. |
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Why is regioselectivity and stereoselectivity important in E2 reactions? |
To react, axial halides and anti hydrogen's react faster, because of less steric hindrence. Products favor trans and more substituted. |
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What is the rate of an E2 reaction? |
Second order Rate = k[Alkylhalide][Base] |
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What types of products are created in E1 and E2 reactions? |
Zaitev products |
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What happens in a Markovnikov Addition reaction? |
A cation is formed in breaking the double bond of an alkene. |
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In a Markovnikov reaction, where does the nucleophile attack? |
The more substituted carbon |
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What is used to catalyze the hydration of alkenes? |
Strong acid, H2SO4 |
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What reactants and solvents are used in the electrophilic addition of HX to alkenes? |
A strong acid (HBr, HCl) and acetic acid |
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What are the reactants and catalysts in ether synthesis? |
An alkene, HxCxOH, and H2SO4 as the catalyst. |
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What solvents are used in oxymercuration and demercuration? |
Hg(OAc)2, THF-H2O NaBH4, OH- |
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What happens in an oxymercuration/demercuration reaction? |
A mercury cation intermediate is formed, and there is Markovnikov Addition of H and OH across a double bond. |
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How are alkenes named? |
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Stability of alkenes |
Energy difference gets bigger between trans and cis the larger the group attached. Trans more stable. For cycloalkenes: small and medium rings are more stable as cis, reduced steric strain |
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What is the temperature of a dehydrohalogenation reaction? |
Very high |
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"The most branched alkene will form" |
Zaitsev's Rule |
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Has to do with which product is easier to make. Is related to either energetic pathway or stability of product. 'Preference' to product made. |
Stereoselection |
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What is this reaction? |
E1: Dehydration of alcohols |
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What reactions are these? |
E2: Dehydrohalogenation of alkyl halides |
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What do stereoelectronic effects have to do with the E2 reaction? |
Axial halides and anti halogens react faster |
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What reaction do 2° alkyl halides go through with a strong base? |
Elimination: E2 |
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1° alkyl halides only go through substitution unless: |
A bulky base, KOC(CH3)3, is used |
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What type of reaction do 2° alkyl halides go through with weakly basic nucleophiles? |
Substitution, SN1 |
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What type of reactions do 3° alkyl halides go through with strong bases? |
E2 |
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What type of reactions do 3° alkyl halides go through in the absence of anionic nucleophiles? |
SN1/E1 |
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Rate of reaction for electrophilic addition of HX to alkenes |
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What mechanism is this? |
Electrophilic addition of HX to alkenes |
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What kind of reaction is this? |
Acid catalyzed hydration of alkenes |
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What mechanism is this? |
Acid catalyzed hydration of alkenes |
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What reaction is this? |
Acid catalyzed ether synthesis from alkenes |
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A system at equilibrium adjusts so as to minimize any stress applied to it |
Le Châtelier's |
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What rection is this? |
Halogenation of alkenes to form vicinal dihalides. Stereospecific reaction, anti addition. Only works with bromine and chlorine |
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What mechanism is this? |
Halogenation of alkenes to form vicinal dihalides |
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What reaction is shown here? |
Halogenation of alkenes in the presence of water to make vicinal halohydrins with OH on the Markovnikov position |
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What mechanism is shown? |
Halogenation of alkenes in the presence of water |
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What products are made in the halogenation of alkenes reaction? |
Trans with the second group on the backside and the enantiomer. |
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What reaction is shown here? |
Hydroboration oxidation |
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What kind of reaction is hydroboration oxidation? |
Anti Markovnikov |
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What reactants and solvents are used in a hydroboration oxidation reaction? |
An alkene, a strong base (OH-), H2O2, and a compound with B and H. |
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Hydroboration oxidation mechanism |
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What is the stereospecific product in hydroboration oxidation? |
Syn |
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What reactions are shown here? |
Hydrogenation of alkenes with the same substituent ( in this case H2) |
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Based on starting materials, which product will be made |
Stereoselection |
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What compound would have the highest heat of hydrogenation? |
The least stable |
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What products are made in a hydrogenation reaction? |
The syn product and enantiomer if chirality centers are made
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What reaction is shown here? |
Preparation of vicinal diols by OsO4 dihydroxylation |
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What reactions are shown here? |
Alkene epoxidation. Enantiomers are made |
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What mechanism is this? |
Hydroboration |
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What mechanism is this? |
Oxidation |
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What reactant is needed in a hydrogenation reaction? |
A metal, Pt, Pd, Ni, or Rh |
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What products are favored in an E2 reaction? |
Trans and more substituted |
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What reactants and catalysts are used in the preparation of vicinal diols by OsO4 dihydroxylation? |
(CH3)3COOH, OsO4 (cat), tertbutanol, -OH |
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Are intermediates formed in the SN2 and E2 reactions? |
No, no rearrangement possible. Called a concerted reaction |
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What are the best nucleophiles? |
Iodides and sulfides. Sulfides the best because they are conjugate bases of strong acids. |
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What way to retrosynthesis arrows face? |
Towards starting materials |
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Memorize |
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What reagents are used in an ozonolysis of alkene reaction? |
Ozone (O3) and H20 or Me2S |
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What happens when H2O is a reagents in the ozonolysis reaction? |
Oxidative conditions, carboxylic acid formed |
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What reagents are used in the Simmons-Smith (or cyclopropanation) reaction? |
CH2I2 and ZnCu and diethyl ether |
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What reaction is shown? |
Ozonolysis of alkenes |
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What happens when zinc is a reagent in ozonolysis? |
The second step is reductive, an aldehyde and formaldehyde are made |
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What reaction is shown? |
Simmons-Smith Reaction |
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What products are made in a Simmons-Simon Reaction? |
Carbenoid, syn addition |
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What are the properties of alkynes? |
Pretty acidic Linear, short bond lengths Low water solubility Similar bpts to alkanes |
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What happens to alkynes in the presence of water and amide ions? |
They can be protonated. This is useful in making long chains through the SN2 mechanism. |
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What happens in reactions with alkynes and secondary or tertiary carbons? |
E2 |
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Mechanism of E2 using alkynes |
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What reaction is shown? |
Formation of alkynes via elimination |
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What reagents are used in the formation of alkynes via elimination? |
NaNH2, NH3, H2O |
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What reaction is shown below? |
Hydrogenation of alkynes |
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What reagents create alkenes from alkynes during hydrogenation? |
H2 and Lindlar Pd |
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What reaction is shown? |
Addition of hydrogen halides to alkynes. Reaction can occur again to make a alkane with geminal dihalides. |
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What mechanism is shown? |
Addition of hydrogen halide to alkyne. Markovnikov reaction |
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What reaction is shown here? |
Hydration of alkynes |
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What products are created in the hydration of alkynes? |
Ketones |
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What reagents are used in the hydration of alkynes when ketones are formed? |
Water, acid, and mercury |
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What reaction is shown? |
Addition of dihalogen to alkynes. Markovnikov reaction |
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What reaction is shown here? |
Ozonolysis of alkynes. Ketones also made during demercuration. |
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Memorize |
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Stability of alkyl radicals |
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How are radicals formed? |
Homolytic cleavage (homolysis) |
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What mechanism is this? |
Methane chlorination |
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What mechanism is shown? |
Halogenation of higher alkanes |
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What happens in a free radical HX addition to alkenes and alkynes with and without peroxides? |
No peroxides, X adds in the Markovnikov position. With peroxides, X adds to anti Markovnikov position |
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Mechanism of free radical addition of HX to alkenes and alkynes with peroxides |
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What product is made when an alkyne reacts with HX in free radical addition? |
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What reagents are used to hydrogenate alkynes using free radicals? |
Na, NH3. Metal ammonia reduction |
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Mechanism for Na-ammonia reduction |
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What reaction is shown here? |
SN1 of allylic halides |
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What mechanism is this? |
SN1 of allylic halides |
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What reaction is shown here? |
SN2 of allylic halides |
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What reagents are used in an SN1 of allylic halides reaction? |
H2O and Na2CO3, or alcohol for ether synthesis |
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What reaction is shown here? |
Allylic free radical halogenation |
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What mechanism is shown here? |
Allylic free radical halogenation mechanism |
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What is the stability of dienes? |
Conjugated > isolated > cumulated |
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How are sigma bonds affected my pi bonds? |
They become shorter |
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What reaction is shown here? |
Addition of HX to conjugated dienes. If cold temps, no rearrangements occur |
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What reaction is shown? |
Halogen addition to conjugated dienes. Leads to mixture but 1,4 dominating |
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What reaction is shown? |
The Diels-Alder reaction |
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How is the Diels-Alder reaction both stereospecific and stereoselecive? |
If a trans groups on the dienophile, groups off cyclohexane have opposite stereochemistry. If cis groups on the dienophile, same stereochemistry and Endo preferred. |
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What reaction is shown here? |
Intramolecular Diels-Alder reaction |
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The Cope and Claisen Rearrangement |
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