Organic Chemistry 3 Test Review

alkyne formula

C_nH_2n-2

Acetylene

• H-C≡C-H

• same as ethyne

• all carbons are sp hybridization

• linear

enynes

compounds with both double and triple bonds

how to name enynes

start on side closest to either double or triple bond, in a tie, go to double bond first

When triple bond is a branch

add -yl (ex. ethynyl)

vicinal dihalide

Halides (X) not on same carbon

geminal dihalide

Halides(X) on the same carbon

For addition reactions, equally substituted means there are..?

2 products

RC≡CR + HX or X₂ →

alkene

RC≡CR + 2HX or 2X₂ →

alkane

mercury catalyzed hydration

• -OH goes to more substituted carbon

• h2SO4,H2O—>HgSO4(bottom)

Hydroboration

• -OH goes to less substituted carbon

• —BH3/H2O2(bottom) —>

Terminal

at end

Acidity order of what will be removed first with a base

-COOH > -OH > yne > ene/ane

only terminal alkenes can act as…?

weak acids

alkyne is the most stable because of more …?

S character (50%)

CH₃CH₃OH

weak acid

CH₃CH₃ONa

strong base

NaH

strong base

NH₃ is a ____ ___, ^-NH₂ is a ____ ____ ____

weak acid; strong conjugate base

carbon is an _____ with a halogen

electrophile

oxidation level formula

(Total # of C-O/C-H/C-X) - (Total # of C-H)

• ex. C=O would count as 2

decrease number of C-H bonds

Oxidation

increase number of C-H bonds

Reduction

trans is more stable than cis because…?

less energy is released and less steric strain

Product of oxidative cleavage when terminal

CO₂

product of oxidative cleavage when not terminal

-COOH (carboxyl acid)

How to tell smth is terminal in oxidative cleavage cut

H at end

How do you plan a synthesis?

Trial and error & retrosynthetically

Tautomerism

an enol interconverts into its isomeric ketone or aldehyde through hydrogen transfer

R≡R —-H₂/Pd-C(bottom)—>

alkane

R≡R —-H₂/Lindlar’s catalyst(bottom)—>

cis alkene

R≡R —^.Na/NH₃(bottom)—>

trans alkene

Pd-C

adam;s catalyst

lindlar’s catalyst

contains heavy metal

substitution reaction product

inversion

elimination reaction product

pair of enantiomers

solvents are either…?

protic or aprotic

protic

forms H⁺ bonds (ex. H₂O, ethanol)

Aprotic

will not form H-bond or have H⁺

leaving groups

• weak bases

• right side of periodic table

• lower on periodic table (bigger)

• same for all reactions

strong nucleophiles

• negative charges are better than neutral

• strong bases

• nucleophilicity improves going right to left and down in the periodic table (polarizability) (ex. -OH < -SH)

less substrated means …?

less steric hinderance

strong base, weak nucleophile, and bulky is better for..?

E₂ reactions

polar protic solvents for SN₁

H₂O > CH₃OH > CH₃CH₃OH > (CH₃)₃COH > CH₃CO₂H

what does SN₂ stand for

Substitution, nucleophilic, and 2 reactants in the rate limiting step

SN₂ substrate

less crowded (less substituted)

SN₂ nucleophile

strong

SN₂ solvent

aprotic (so it doesn’t attach to nucleophile)

what happens to the rate when the nucleophile or alkyl halide doubles in a SN₂ reaction

reaction rate doubles

how many steps in SN₂ reaction?

one

SN₂ graph

SN₁ graph

SN₁ Substrate

more crowded (more substituted)

SN₁ Nucleophile

weak

SN₁ Solvent

protic (to stabilize intermediate/carbocation)

how many steps in a SN₁ reaction

two (leaving group leaves in 1st, carbocation forms trigonal planar geometry in 2nd)

what happens to reaction rate in a SN₁ reaction if you double the nucleophile

no change because nucleophile not in rate limiting step

what happens to reaction rate in a SN₁ reaction if you double alkyl halides

doubles

1st in a reaction

rate limiting step (slowest)

which substrates are the best for SN₂ reactions

methyl halides (CH₃-X)

more hydrogen means…?

more reactive and less crowded

less reactive means…?

slower reaction

Zaitsev’s rule

The stability of alkenes increases with substitution, thus the major product in beta elimination has the more substituted double bond

what product does MCPBA give?

epoxide

vinyl halide

X directly attached to doubly bonded carbon

aryl halide

benzene ring

allylic halide

not directly (carbon in between) X and double bond

benzylic halide

benzene ring with CH₃

alpha carbon

carbon directly connected to halogen

beta carbon

carbon connected to alpha carbon

elimination reaction product

alkenes

identical groups on the same doubly bonded carbon means..?

no cis or trans (no stereoisomers)

what happens in E₁ reactions

leaving group leaves and forms cation

what does an E₂ reaction need

strong base and antiperiplanar geometry

what happens in E₂ reactions

Base takes proton, leaving group leaves

E₂ solvent

aprotic solvent

E₂ substrate

tertiary substrate (because more substrated alkene produced)

more reactive in E₂ reaction

tertiary

base in E₁

weak (because carbocation present)

Solvent in E₁

polar protic

substrate in E₁

tertiary substitution (because more substrate alkene produced)

radical reaction steps

initiation, propogation, termination

initiation step in radical reaction needs..?

UV or heat

allylic radical

more stable than tertiary (resonance)

tertiary radical

more reactive than secondary and primary

allylic position

radical not on doubly bonded carbon

Grignard reagents

organometallic compounds that contain a carbon-magnesium bond. Formally the Mg salt of a carbonic acid, and thus a carbon anion, a strong base.

• Reaction of R-X with Mg in ether or THF

• product of R-MG-X is an organometallic compound (alkyl-metal bond

• X= Cl,Br,I

• R= alkyl

• electrophilic to basic and nucleophilic

• carbon is partial positive with X but partial negative with Magnesium

leaving group examples

OH^-/NH₂ ^-/OR^- < F- < Cl- < Br- < I- < TosO-

protic and aprotic examples

CH₃OH (protic) < H₂O (protic) < DMSO (aprotic) < DMF (aprotic) < CH₃CN (aprotic) < HMPA (aprotic)

nucleophile strength from least to most

H₂O < CH₃CO₂^- < NH₃ < CL^- < OH^- < CH₃O < I^- < CN^- < HS^-

R-X have a higher boiling point than …?

alkanes (increases with an increased size of X or the chain)