Organic Chemistry Substitution and Elimination Reactions

Which reactions results in inversion of configuration?

Sn2

__________________ reactions feature a nucleophile in the rate-determining step

Sn2

Carbocation rearrangements are possible in ______________ reactions

Sn1 and E1

______________________ reactions results in both inversion and retention of configuration (racemization)

Sn1

Weak nucleophiles are ok.

Sn1

Sn1 or Sn2 reactions require strong nucleophiles

Sn2

If you have a tertiary halide then you can't do an Sn1 or Sn2 reaction?

Sn2

If you have a primary halide then you can't do an Sn1 or Sn2 reaction?

Sn1

Electrophiles that are more or less substituted react more strongly with nucleophiles in Sn2 reactions.

less substituted (CH3 > primary > secondary)

Electrophiles that are more or less substituted react more strongly with nucleophiles in Sn1 reactions

more substituted (tertiary > secondary)

Which substitution reaction results in the formation of ions?

Sn1

If the solvent is aprotic is the reaction Sn1 or Sn2?

Sn2

If the solvent is protic is the reaction Sn1 or Sn2?

Sn1 mostly, Sn2 prefers polar aprotic solvent but can do protic solvent

Which substitution reaction has the leaving group leave in the slow step?

Both Sn1 and Sn2

The solvents listed: DMSO, acetone, DMF, acetonitrile, ether, THF are polar aprotic or protic?

aprotic

Rearrangements are possible for Sn1 or Sn2 reactions?

Sn1

Inversion possible for Sn2 or Sn1 reactions?

Sn2 (Sn1 feature racemization)

Strong or weak nucleophiles typically are anions.

Strong

Strong or weak nucleophiles are typically neutral

weak

Strong nucleophiles are more or less electronegative?

less electronegative

Strong nucleophiles are larger or smaller in size?

larger

The conjugate base is always a stronger or weaker nucleophile?

stronger (nucleophilicity increases with increasing electron density on an atom)

Nucleophilicity increases with increasing or decreasing electronegativity?

decreasing electronegativity (CH3- > NH2- > OH- > F- the less electronegative the atom the less tightly the electrons are held)

NaOCH3 (any NaOR), LiCH3 (any RLi), NaOH or KOH, NaCN or KCN are examples of strong or weak nucleophiles?

strong

H2O, ROH, H2S, RSH are examples of strong or weak nucleophiles?

weak

A molecule that has a negative charge that is delocalized is a strong or weak nucleophile?

weak

A molecule that has a negative charge that is not delocalized is a strong or weak nucleophile?

strong

In protic or aprotic solvent nucleophile strength increases going down the periodic table

protic (Sn1) (Reason: Capacity for hydrogen bonding is highest at the top of the periodic table, with increasing hydrogen bonding nucleophile becomes more hindered)

Strong or weak nucleophiles are resonance stabilized and contain lone pairs typically?

weak

In protic or aprotic solvents nucleophile strength increases going up the periodic table.

aprotic

Why is a more substituted carbocation favorable for an Sn1 reaction?

Because it is stable enough to form an intermediate to be attacked by the nucleophile. A secondary carbocation would not last as long as a tertiary and a primary carbocation would not be stable enough to form.

Electrophiles that are more or less substituted react more strongly with nucleophiles in E2 reactions.

More substituted (tertiary > secondary > primary)

Electrophiles that are more or less substituted react more strongly with nucleophiles in E1 reactions?

More substituted (tertiary > secondary, primary alkanes don't react in E1)

E2 reactions require a strong base or weak base

strong base

E1 reactions require strong base or weak base

weak base

What kind of solvent is required for an E2 reaction?

polar aprotic is preferred but polar protic can work

What kind of solvent is required for an E1 reaction?

polar protic

A primary carbocation that is allylic or benzylic is better or worse for substitution reactions?

better

Allylic halides react faster or slower with SN2 reactions?

faster

Tert-butoxide is an example of what type of base and what type of nucleophile?

strong base/poor nuc (sterically hindered)

A strong nucleophile features ________ reaction as the major reaction for primary carbons and methyls.

Sn2

When a strong nucleophile is used which reactions can occur for methyl, primary and secondary carbons?

Sn2 is major

When a strong nucleophile or strong base is used which reactions can occur for secondary carbons?

E2 and Sn2

When a strong nucleophile or strong base is used which reactions can occur for tertiary carbons?

E2 is major (Sn2 can't occur)

When a weak nucleophile or weak base is used which reactions can occur?

Sn1 or E1 for tertiary and secondary carbons only (tertiary > secondary)

A strong nucleophile that is a weak base are used in which reactions?

Sn2

Which type of reactions require a strong base/strong nucleophile?

Sn2 and E2

Negatively charged nucleophiles/bases tend to perform what types of reactions?

Sn2 and E2

E2 eliminations afford a more or less substituted alkene?

more substituted (Zaitsev product)

E2 eliminations afford a more or less substituted alkene if F- is leaving group?

less substituted (Hofmann product)

E2 eliminations afford a more or less substituted alkene if bulky base such as tert-butoxide is used with tertiary halide?

less substituted (Hofmann product)

________________ solvents cannot hydrogen bond with themselves

Polar aprotic (Lack O-H, N-H, F-H bonds)

______________ solvents can hydrogen bond with themselves

Polar protic

Hydrogen bonding solvents tend to decrease the reactivity of ____________________.

nucleophiles (Bad for Sn2)

___________________ solvents serve as the solvent for their conjugate base

Polar protic (Sn1) ex - NH3/NH2-

NaN3 and DMF. What kind of nucleophile and solvent are these?

strong nucleophile and weak base (DMF is polar aprotic =>SN2 likely)

NaSH in DMSO are what kind of nucleophile and solvent?

strong nucleophile, weak base (DMSO aprotic solvent =>SN2 likely)

Polar protic solvents tend to favor E2 or SN2?

E2

Polar aprotic solvents tend to favor E2 or SN2?

SN2

Use of a bulky base in an elimination reaction results in a Zaitsev product or anti-Zaitsev product?

anti-Zaitsev (less substituted alkene)

EtOH is what kind of solvent and base?

Weak solvent, weak base

Solvents increase in strength on the periodic table in rows going from left to right or right to left?

right to left

Nucleophile strength increases on the periodic table in rows going from left to right or right to left?

right to left

A nucleophile with a negative charge on a more or less electronegative atom is a stronger nucleophile?

less electronegative

Solvolysis is a common type of ___________ reaction

Sn1

Negatively charged ions tend to be stronger or weaker nucleophiles than neutral species?

Stronger (Good for SN2)

Elimination reactions require that the electrophile (contains leaving group) have at least _____________ # of carbons.

2

If you have a tertiary halide, polar protic solvent, and a strong base? What type of reaction is this?

E2 (Zaitsev and anti-Zaitsev product forms)

A nucleophile that is more basic is a stronger or weaker base?

weaker base

A leaving group that has the negative charge stabilized on a larger or smaller atom is a better leaving group?

larger (ex: I- better leaving group than Br-)

A good leaving group is a strong or weak base?

weak base

Is fluorine a good or poor leaving group?

Poor

Is methanol a good or weak nucleophile?

weak

Are negatively charged halogens strong nucleophiles?

No (Even though most other anions are strong nucleophiles)

An SN1 reaction has a uni-molecular or bi-molecular rate-determining step?

uni-molecular (The 1 in Sn1 stands for uni-molecular)

An E1 reaction has a uni-molecular or bi-molecular rate-determining step?

uni-molecular (The 1 in E1 stands for uni-molecular)

An SN2 reactions has a uni-molecular or bi-molecular rate-determining step?

bi-molecular

An E2 reactions has a uni-molecular or bi-molecular rate-determining step?

bi-molecular

In Sn1 reactions, addition of ____________ facilitates carbocation formation.

AgNO3

In ________ reactions the H and X (leaving group should be anti-periplanar/anti-coplanar (meaning H and X are trans to each other)

E2

In E2 reactions, the least substituted (Hofmann product) is formed if _____ is the leaving group.

F-

In E2 reactions, the least substituted (Hofmann product) is formed if a _________ is used with a tertiary halide.

bulky base

E1 or E2 or both reactions involve a carbocation intermediate?

E1 (So does Sn1)

The ________ reaction involves the formation of the pentavalent transition state.

Sn2

A negative charge on any atom besides oxygen tends to be a __________ nucleophile but a ________ base

strong; weak

In an E2 reaction if a less substituted alkene is formed from a leaving group anti-periplanar to a beta hydrogen or another possible more substituted alkene could be formed form a leaving group that is not anti-periplanar to the beta hydrogen, which product will form?

less substituted (due to anti-periplanar hydrogen relative to leaving group)

A carbocation that is aromatic, non-aromatic, or anti-aromatic will react faster in an Sn1 reaction?

aromatic (the carbocation will be more stable)

Is OH a good leaving group?

No (Because -OH readily gets protonated, strong base)