Term
| Alkyl halides undergo substitution reactions with ____ |
|
Definition
|
|
Term
| alkyl halides undergo elimination reactions with ____ |
|
Definition
|
|
Term
| bronsted lowry bases are ____ |
|
Definition
|
|
Term
|
Definition
|
|
Term
| nucleophiles tend to be ___ |
|
Definition
|
|
Term
| because these substitution reactions involve electron rich nucleophiles, they are called ___ |
|
Definition
| nucleophilic substitution reactions |
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|
Term
| nucleophilic substitution reactions are ___ |
|
Definition
| lewis acid-base reactions |
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|
Term
| note that all atoms originally bonded to the nucleophile ___ after substitution occurs |
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Definition
|
|
Term
| when the substitution product bears a positive charge and also contains a proton bonded to ___; the initial substitution product readily loses a proton in a bronsted-lowry acid-base reaction forming a ____ |
|
Definition
|
|
Term
| in comparing two leaving groups, the better leaving group is the ____ |
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Definition
|
|
Term
| in the periodic table; basicity decreases from ____ |
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Definition
| left to right across a row, and down a column |
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|
Term
| in the periodic table, basicity increases ____. |
|
Definition
| from right to left across a row, and up a column |
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|
Term
| all good leaving groups are ___ bases with ___ conjugate acids having ___ pKa values. |
|
Definition
|
|
Term
| equilibrium favors the products of nucleophilic substitution when the ____ |
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Definition
| leaving group is a weaker base than the nucleophile |
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Term
| nucleophiles and bases are structurally similar in that they both have a ___; they are different in ___ |
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Definition
| lone pair or a pie bond; what they attack |
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Term
| bases attack ___; nucleophiles attack ____ |
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Definition
| protons; other electron deficient deficient atoms (usually carbons) |
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Term
| a strong ___ is generally a strong ___ |
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Definition
|
|
Term
| for two nucleophiles with the same nucleophilic atome; the ___ is the stronger nucleophile |
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Definition
|
|
Term
| a ___ is always stronger than its conjugate acid |
|
Definition
| negatively charge nucleophile |
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|
Term
| right to left across a row of the periodic table, _____ as ____. |
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Definition
| nucleophilicity increases as basicity increases |
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|
Term
| nucleophilicity does not parallel basicity when ___ becomes important |
|
Definition
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|
Term
| ___ is a decrease in reactivity resulting from the presence of bulky groups at the site of the reaction |
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Definition
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|
Term
| steric hindrance decreases ___ but not ___ |
|
Definition
| nucleophilicity; basicity |
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|
Term
| sterically hindered bases that are poor nucleophiles are called ____ |
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Definition
|
|
Term
| nucleophilicity depends on the ___ used in a substitution reaction |
|
Definition
|
|
Term
| there are two main kinds of polar solvents: ___ and ___ |
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Definition
| polar protic solvents; polar aprotic solvents |
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|
Term
| polar protic solvents are capable of ____ |
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Definition
| intermolecular hydrogen bonding |
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Term
| polar protic solvents solvate both ___ and ___ well |
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Definition
|
|
Term
| in polar protic solvents, cations are solvated by ___ interactions |
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Definition
|
|
Term
| in polar protic solvents, anions are solvated by ___ |
|
Definition
|
|
Term
| in polar protic solvents, ___ increases down a column of the periodic table as the size of the ___ increases. This is opposite to ___ |
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Definition
| nucleophilicity; anion; basicity |
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|
Term
| thus, ___ increases down a column |
|
Definition
|
|
Term
| polar aprotic solvents also exhibit ___, but are incapable of ___ |
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Definition
| dipole-dipole interactions; hydrogen bonding |
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|
Term
| polar aprotic solvents solvate ___ |
|
Definition
|
|
Term
| in polar aprotic solvents; cations are solvated by ___; anions are ___ |
|
Definition
| ion-dipole interactions; not well solvated because the solvent cannot hydrogen bond to them |
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|
Term
| in polar aprotic solvents; the stronger ___ is the stronger ____ |
|
Definition
|
|
Term
| it is generally true that the stronger ___ is the stronger ____ |
|
Definition
|
|
Term
| in polar protic solvents, ___ increases with increasing size of the ____ |
|
Definition
| nucleophilicity; anion (opposite to basicity) |
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|
Term
| ___ decreases nucleophilicity without decreasing basicity. |
|
Definition
|
|
Term
| what are the 3 possibilities for the bonds in nucleophilic substitution. |
|
Definition
1) bond breaking and bond making occur at the same time
2) bond breaking occurs before bond making
3) bond making occurs before bond breaking, but since this violates the octet rule it can be disregarded |
|
|
Term
| when bond breaking and bone making occur at the same time generate a ____; while when bond breaking occurs before bond making generates a ____. |
|
Definition
| one step mechanism; two step mechanism |
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|
Term
| when bond breaking and bond making occur simultaneously, the rate equation is ____ |
|
Definition
|
|
Term
| when bond breaking occurs before bond making, the rate equation is ___ |
|
Definition
|
|
Term
| when the rate equation depends on the concentration of both reactants, the rate equation is ___ |
|
Definition
|
|
Term
| because the one step mechanism is second order, this suggests a ___ |
|
Definition
|
|
Term
| when the rate equation depends on the concentration of only one reactant, the rate equation is ___ |
|
Definition
|
|
Term
| this first order rate equation suggests a ____ in which the rate determining step ____ |
|
Definition
| two-step mechanism; involves the alkyl halide only |
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|
Term
| a second order rate equation = ____ = ___ |
|
Definition
| one-step mechanism; Sn2 (substitution nucleophilic bimolecular) |
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|
Term
| what are the two possibilities for what direction the nucleophile approaches the substrate in an Sn2 reaction: |
|
Definition
| frontside attack; backside attack |
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|
Term
| in a frontside attack; the nucleophile approaches from the ___ as the leaving group |
|
Definition
|
|
Term
| in a backside attack; the nucleophile approaches from the ___ the leaving group |
|
Definition
|
|
Term
| a front side attack results in ___ around the sterogenic center |
|
Definition
| retention of configuration |
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|
Term
| a backside attack results in ___ around the stereogenic center |
|
Definition
| inversion of configuration |
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|
Term
| the products of frontside and backside attacks are ___ compounds, and are ___ |
|
Definition
|
|
Term
| all Sn2 reactions proceed with a ___ of the nucleophile, resulting in ___ at a stereogenic center. |
|
Definition
| backside attack; inversion of configuration |
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|
Term
| as the number of R groups on the carbon with the leaving group ___, the rate of the Sn2 reaction ____. |
|
Definition
|
|
Term
| ___ and __ undergo Sn2 reactions with ease |
|
Definition
| methyl and one degree alkyl halides |
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|
Term
| ___ undergo Sn2 reactions more slowly |
|
Definition
|
|
Term
| ____ do not undergo Sn2 reactions |
|
Definition
|
|
Term
| ____ the number of R groups on the carbon with the leaving group, ____ crowding in the transition state, ____ the rate of an Sn2 reaction |
|
Definition
| increasing; increases; decreasing |
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|
Term
| The Sn2 reaction is fastest with ____ |
|
Definition
|
|
Term
give the characteristics of the Sn2 mechanism for
Kinetics:
Mechanism:
Stereochemistry:
Identity of R: |
|
Definition
Kinetics: second-order kinetics
Mechanism: one step
Stereochemistry: backside attack of the nucleophile, inversion of configuration at a stereogenic center
identity of R: unhindered halides react fastest |
|
|
Term
| first order kinetics = ___ = ___ |
|
Definition
| two step mechanism = Sn1 (substitution nucleophilic unimolecular) |
|
|
Term
| this suggests that the Sn1 mechanism involves ____ step, that the slow step is ___, and the ____. |
|
Definition
| more than one step; unimolecular involving the only the alkyl halide; identity and concentration of the nucleophile have no effect on the reaction rate. |
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|
Term
| a two step mechanism occurs when ___ |
|
Definition
| bond breaking occurs before bond making |
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|
Term
| the two key features of the Sn1 mechanism are that the ___ and that ___. |
|
Definition
| mechanism has two steps; carbocations are formed as reactive intermediates |
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|
Term
| a carbocation (___) is ___ hybridized and is ____. It contains a vacant __ orbital extending above and below the plane |
|
Definition
| (with three groups around the C); sp2, trigonal planar; p |
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|
Term
| ___ is the formation of equal amounts of two enantiomeric products from a single starting material |
|
Definition
|
|
Term
| Sn1 reactions proceed with ____ at a single stereogenic center |
|
Definition
|
|
Term
| As the number of R groups on the carbon with the leaving ____, the rate of an Sn1 reaction ____ |
|
Definition
|
|
Term
| ___ undergo Sn1 reactions rapidly |
|
Definition
|
|
Term
| ___ undergo Sn1 reactions more slowly |
|
Definition
|
|
Term
| ___ and ___ do not undergo Sn1 reactions |
|
Definition
| methyl and 1 degree alkyl halides |
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|
Term
give the following characteristics of an Sn1 mechanism:
kinetics:
mechanism:
stereochemistry:
identity of R: |
|
Definition
Kinetics: first order kinetics, rate=[RX]
Mechanism: two steps
Stereochemistry: trigonal planar carbocation intermediate, racemization at a single stereogenic center
Identity of R: more substituted halides react fastest |
|
|
Term
| carbocations are classified as ___ by the number of R groups bonded to the charged carbon atom |
|
Definition
| primary, secondary, or tertiary |
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|
Term
| as the number of R groups on the positively charged carbon atom ___, the stability of the carbocation ___. |
|
Definition
|
|
Term
| ___ effects are electronic effects that occur through sigma bonds |
|
Definition
|
|
Term
| ___ groups are electron donating groups that stabilize a positive charge |
|
Definition
|
|
Term
| as R groups successively replace the H atoms in CH3+, ____ |
|
Definition
| the positive charge is more dispersed on the electron donor R groups, and the carbocation is more stabilized. |
|
|
Term
| ___ number of electron donating R groups, ___ carbon stability |
|
Definition
|
|
Term
| spreading out charge by the overlap of an empty p orbital with an adjacent sigma bond is called ____ |
|
Definition
|
|
Term
| the rate of an ___ reaction increases as the number of R groups on the ____ increases |
|
Definition
| Sn1; carbon with the leaving group |
|
|
Term
| the stability of a ___ increases as the number of R groups on the ___ increases |
|
Definition
| carbocation; positively charged carbon |
|
|
Term
| thus, the rate of an Sn1 reaction ___ as the stability of the carbocation ___ |
|
Definition
|
|
Term
| transition states in endothermic reactions resemble the ___ |
|
Definition
|
|
Term
| transition states in exothermic reactions resemble the ___ |
|
Definition
|
|
Term
| in an endothermic reaction, the ___ forms faster |
|
Definition
|
|
Term
| in an exothermic reaction, the ___ |
|
Definition
| more stable product may or may not form faster because Ea is similar for both products. |
|
|
Term
| in the Sn1 reaction, the rate determining step is the ____ |
|
Definition
| formation of the carbocation, an endothermic reaction |
|
|
Term
| the most important factor in determining whether a reaction follows the Sn1 or Sn2 mechanism is the ____ |
|
Definition
| identity of the alkyl halide |
|
|
Term
| increasing alkyl substitution favors ___ |
|
Definition
|
|
Term
| decreasing alkyl substitution favors ___ |
|
Definition
|
|
Term
| methyl and one degree halides undergo ___ |
|
Definition
|
|
Term
| three degree alkyl halides undergo ___ |
|
Definition
|
|
Term
| two degree alkyl halides undergo ___ |
|
Definition
| both Sn1 and Sn2 reactions |
|
|
Term
| strong nucleophiles present in high concentration favor ___ |
|
Definition
|
|
Term
| weak nucleophiles favor ___ |
|
Definition
|
|
Term
| the most common nucleophiles in Sn2 reactions ___; the most common nucleophiles in Sn1 reactions are ___ |
|
Definition
| bear a net negative charge; weak nucleophiles such as H2O and ROH |
|
|
Term
| the strong nucleophile favors an ___ reaction, which occurs with a ___ attack, resulting in an ____. |
|
Definition
| Sn2; backside; inversion of configuration |
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|
Term
| the weak nucleophile favors an ___ reaction, which occurs by the way of ___, and exhibits ____ |
|
Definition
| Sn1 reaction; intermediate carbocation, racemization |
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|
Term
| a better leaving group increases the rate of ____ |
|
Definition
| both Sn1 and Sn2 reactions |
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|
Term
| for alkyl halides, the leaving group ability increases ___ |
|
Definition
|
|
Term
| ____ solvents are especially good for Sn1 reactions |
|
Definition
|
|
Term
| ____ are especially good for Sn2 reactions |
|
Definition
|
|
Term
| methyl and 1 degree alkyl halides display a ___ mechanism; and are favored by ___ and ____ |
|
Definition
| Sn2 mechanism; strong nucleophiles; polar aprotic solvents |
|
|
Term
| 3 degree alkyl halides display a ___ mechanism, and are faved by ___ and ___ |
|
Definition
| Sn1; weak nucleophiles, polar protic solvents |
|
|
Term
| 2 degree alkyl halides display a ___ mechanism, which depends on ___ or ___. |
|
Definition
| Sn1 or Sn2; strong nucleophiles favor the Sn2 mechanism over the Sn1 mechanism; protic solvents favor the Sn1 mechanism and aprotic solvents favor the Sn2 mechanism |
|
|
Term
| ___ is the systematic preparation of a compound from a readily available starting material by one or many steps. |
|
Definition
|
|
Term
| all ___ reactions involve loss of elements from the starting material to form a new pie bond in the reaction |
|
Definition
|
|
Term
| alkyl halides undergo elimination reactions with ___. |
|
Definition
|
|
Term
| removal of the elements of HX, called ___, is one of the most common methods to introduce a pie bond and prepare an alkene |
|
Definition
|
|
Term
| dehydrohalogenation is an example of __ elimination |
|
Definition
|
|
Term
| the __ carbon is bonded to the leaving group X, and the ___ carbon adjacent to it. |
|
Definition
|
|
Term
| the base removes a proton on the ___ carbon. |
|
Definition
|
|
Term
| the electron pair in the ___ bond forms the new pie bond between the alpha and beta carbons |
|
Definition
|
|
Term
| The electron pair in the C-X bond ends up on the ___ |
|
Definition
|
|
Term
| the sp3 carbon bonded to the leaving group is the ___ carbon |
|
Definition
|
|
Term
| the ___ bond, formed by end-on overlap of the two sp2 orbitals, lies in the plane of the molecule |
|
Definition
|
|
Term
| the ___ bond, formed by side-by-side overlap of two 2p orbitals, lies perpendicular to the plane of the molecule |
|
Definition
|
|
Term
| a ___ alkene has one R group bonded to the carbons of the double bond |
|
Definition
|
|
Term
| a ___ alkene has two R groups bonded to the carbons of the double bond. |
|
Definition
|
|
Term
| the ___ isomer has two groups on the same side of the double bond. |
|
Definition
|
|
Term
| the ___ isomer has two groups on the opposite sides of the double bond |
|
Definition
|
|
Term
| stereoisomers on a C=C are possible when: |
|
Definition
| the two groups on the first C are different from each other, and the the two groups on the second C are also different from each other. |
|
|
Term
| ___ alkenes are generally more stable than ___ alkenes |
|
Definition
|
|
Term
| the stability of an alkene increases as ___ |
|
Definition
| the number of R groups bonded to it increases |
|
|
Term
| sp2 hybridized carbon atoms are more able to ___ electron density, and sp3 hybridized carbon atoms are more able to ___ electron density |
|
Definition
|
|
Term
| increasing the number of electron donating R groups on a carbon atom able to accept electron density makes the alkene ___ |
|
Definition
|
|
Term
| trans alkenes are more stable than cis alkenes because they have ____ |
|
Definition
|
|
Term
| increasing ___ stabilizes an alkene by an electron donating inductive effect |
|
Definition
|
|
Term
| the E2 mechanism is a ____ |
|
Definition
|
|
Term
| the E1 mechanism is a ____ |
|
Definition
|
|
Term
| an E2 reaction exhibits ___ kinetics |
|
Definition
|
|
Term
| in the E2 rate equation; both the ___ and ___ appear in the reaction |
|
Definition
|
|
Term
| in an E2 reaction; all the bonds ____ |
|
Definition
| are broken and formed in a single step |
|
|
Term
| for E2 elimination to occur, there must be at least one hydrogen on a ____ |
|
Definition
|
|
Term
| the rate of the E2 reaction ___ as the strength of the base increases |
|
Definition
|
|
Term
| because the bond to the leaving group is partially broken in the transition state, the ____ the faster the reaction |
|
Definition
|
|
Term
| a better leaving group is a ___ |
|
Definition
|
|
Term
| as the number of R groups on the carbon with the leaving group increases, the rate of an E2 reaction ___ |
|
Definition
|
|
Term
| an E2 reaction is fastest with a ___ carbon, while Sn2 reactions are fastest with a ___ |
|
Definition
|
|
Term
| increasing the number of R groups on the carbon with the leaving group forms more _____ in E2 reactions |
|
Definition
| highly substituted, and more stable alkenes |
|
|
Term
| ___ solvents increase the rate of an E2 reaction |
|
Definition
|
|
Term
characteristics of an E2 mechanism
kinetics:
mechanism:
Identity of R:
Base:
Leaving group:
solvent: |
|
Definition
kinetics= second order
mechanism= one step
identity of R: R3CX>R2CHX>RCH2X
Base: favored by strong bases
Leaving group: Better leaving group = faster reaction
Solvent: favored by polar aprotic solvents |
|
|
Term
| what is the zaitsev rule? |
|
Definition
| the major product in Beta elimination has the more substituted double bond |
|
|
Term
| a reaction is ___ when it forms predominantly or exclusively one stereoisomer when two or more are possible |
|
Definition
|
|
Term
| The E2 reaction is ___ because one stereoisomer is formed preferentially |
|
Definition
|
|
Term
| an E1 mechanism exhibits ___ kinetics |
|
Definition
|
|
Term
|
Definition
|
|
Term
| the slow step in an E1 reaction is unimolecular and involves only the ____ |
|
Definition
|
|
Term
| the E1 reaction is a ___ reaction |
|
Definition
|
|
Term
| the E1 reaction is a two step reaction because ____ |
|
Definition
| the bond to the leaving group breaks first before the pie bond is formed |
|
|
Term
| in an ___ reaction, the leaving group comes off before the beta proton is removed, and the reaction occurs in two steps |
|
Definition
|
|
Term
| in an ___ reaction, the leaving group comes off as the beta proton is removed, and the reaction occurs in one step |
|
Definition
|
|
Term
| the rate of an E1 reaction ___ as the number of R groups on the carbon with the leaving group increases |
|
Definition
|
|
Term
| ___ bases favor E1 reactions |
|
Definition
|
|
Term
| ___ bases favor E2 reactions |
|
Definition
|
|
Term
| E1 reactions are ____; favoring formation of the more substituted, more stable alkene |
|
Definition
|
|
Term
characteristics of E1 mechanism
kinematics:
mechanism:
identity of R:
Base:
Leaving group:
Solvent: |
|
Definition
kinematics: first order
mechanism: two steps
identity of R: more substituted halides react fastest R3CX>R2CHX>RCH2X
Base: favored by weaker bases such as H20 and ROH
leaving group: a better leaving group makes the reaction faster
solvent: polar protic solvents |
|
|
Term
| ___ and ___ have exactly the same first step; the formation of a carbocation |
|
Definition
|
|
Term
| in a __ reaction, a nucleophile attacks the carbocation, forming a substitution product |
|
Definition
|
|
Term
| in an __ reaction, a base removes a proton, forming a new pie bond |
|
Definition
|
|
Term
| The H and X atoms can be oriented on the same side of the molecule; this geometry is called ____ |
|
Definition
|
|
Term
| The H and X atoms can be oriented on the opposite sides of the molecule. This geometry is called ____ |
|
Definition
|
|
Term
| E2 reactions occur most in the ___ geometry |
|
Definition
|
|
Term
| an anti periplanar has a ___ confirmation |
|
Definition
|
|
Term
| a syn periplanar has an ___ confirmation |
|
Definition
|
|
Term
| the ___ is the most important factor in determining the mechanism for elimination. |
|
Definition
|
|
Term
| strong bases favor ___; weak bases favor ___ |
|
Definition
|
|
Term
| good nucleophiles that are weak bases favor ___ over ___ |
|
Definition
| substitution over elimination |
|
|
Term
| bulky, nonnucleophilic bases favor ___ over ___ |
|
Definition
| elimination over substitution |
|
|
Term
| E2 reactions can occur with ___ alkyl halides |
|
Definition
|
|
Term
| E1 mechanisms cannot occur with ___ alkyl halides |
|
Definition
|
|
