Orgo Test 2 Flashcards
2 Carbon Alkene
Ethene
3 Carbon Alkene
Propene
4 carbon alkene
Butene
When naming an Alkene how do you number the parent chain?
Start with the side that reaches the double bond first
BOTH PARTS OF THE DOUBLE BOND MUST BE INCLUDED IN THE CHAIN
Cis Stereochemistry
Identical substitute to stick of the same side
Trans stereochemistry
Identical substituents stick off opposite sides of the double bond
Z stereochemistry
High priority substituents are on the same side “ze zame zide” 😂😂
E stereochemistry
High priority substituents are on opposite sides of the double bond
Diene
Suffix used when an Alkene has 2 double bonds
Triene
Suffix when an Alkene has 3 double bonds
Protonation
Use electrons from the double bond to form a bond with the proton (H) in the hydrohalic acid
Carbocation
Positively charged carbon
Tertiary (3 degree) cation
3+ carbon substituents….most stable
Secondary (2 degree) cation
2 carbon substituents…..more stable than primary (1degree) cations
Primary (1 degree) cation
1 carbon substituent…least stable
Adding a hydrohalic acid to an Alkene involves…
Markovnikov addition
Markovnikov’s rule
The proton prefers to attach to the less substituted carbon
Doing this leaves the more substituted carbon with the positive charge
The most stable carbocation reacts…
Fastest
Halogenation
Addition of Br2 or Cl2
Hydrogenation
Addition of H2
Hydrogenation and cis products
occurs when alkene interacts with activated H atoms on the surface of a catalyst so the H atoms add to the same side of the double bond (called syn addition) resulting in cis product
Halogenation and trans products
two halides add to opposite sides of the double bond (anti addition)
halohydrin
one halide and one alcohol [OH]
dihalide
molecule with two halide groups
R and S configuration
R –> clockwise S–> counterclockwise
Tip: when driving a car if you turn the steering wheel clockwise you’re going right (R)
Group Priority
1st priority goes to the atom/molecule with the highest atomic number
Priority for identical 1st atoms ex: CO and CH
CO has higher priority bc O has a higher atomic number than H
Priority for chains ex: CC and CCC
CCC has higher priority bc its a longer chain, this applies to all atoms except F
OH-R
alcohol
SH-R
thiol
NH2-R
amine
R-OR
ether
R-COO-R
ester
R-CtriplebondN
nitrile
enatinomer
non-identical, mirror image structures, not superimposable
stereoisomers
different orientations of atoms in space
Diastereomers
any stereoisomer that is not identical –> NOT MIRROR IMAGES
Mechanism of halogenations
the double bond attacks a halide while the halide attacks the carbon (looks like a circle) the one halide is connected to both carbons from the broken double bond
the other halide then attacks the backside of the positively charged halide breaking one of the halide carbon bonds resulting in each carbon for the double bond being single bonded to a halide in trans stereochemistry
meso
superimposable –> if they were laid on top of each other they would be identical
mechanism of hydrogenation
double bond breaks and the H attach bolded and with cis orientation –> the original substituents on the carbon double bond become dashed
hydride shift
a hydrogen on an adjacent more highly substituted carbon moves to the cationic (+) carbon (hydride shifts are preferred over alkyl shifts)
alkyl shift
if no hydrogens are on the adjacent carbon, an R group (like CH3) moves over to the positive carbon
after a hydride or alkyl shift remember the C without a full octet has a
positive charge
Naming alkynes
the parent chain has the suffix yne and is numbered with the lowest possible number
substituents end with yl unless they’re halogens in which case o ex: bromo
if there is an alkene and an alkyne the parent chain is named with the suffix
enyne
H2/Lindlar catalyst
reduces alkynes to cis alkenes
Na/NH3 reagents
reduces alkynes to trans-alkenes with Trans Hydrogens
H2/Pd(C) or H2/Pt catalysts
highly active catalysts and reduce alkynes to alkanes not stopping at alkenes
Adding water to alkynes
add water across the triple bond to form the unstable enol
perform tautomerization that converts the enol into the carbonyl form
tautomerization
proton transfer and double bond shift take place
the proton on oxygen transfers to the adjacent carbon while the double bond changes from C=C to C=O
enol
alcohol-substituted alkene –> unstable and rapidly rearrange through tautomerization
Markovnikov addition with oxymercuration reaction (no B)
OH adds to more substituted carbon
anti-Markovnikov addition with borane reaction
OH adds to less substituted carbon
creating alkynes
reactions require terminal alkyne and a very strong base (usually 2NaNH2 or 2NaOH)
the halides get kicked off and a triple bond is formed, if there is already a triple bond and youre using only a strong acid add an ethyl to the triple bond if there is a strong acid and a solvent add whatever CH(n) in the 2nd solvent to the triple bond
ex: NaNH2 and CH3Br add CH3 to the triple bond
double dehydrohalogenation reactions
double-elimination reaction –> kicks off 2 halides and 2 H
Sn1
prefers tertiary and secondary (okay) Has NH or OH Poor nucleophile okay mix of stereoisomers rate = k[substrate]
Sn2
prefers methyl and primary substrates prefers less steric crowding no NH or OH bonds good nucleophile needed product has inverted stereochemistry rate = k[substrate][nucleophile]
secondary substrates
look for strength of nucleophile
negatively charged nucleophiles and strong bases (OH) are for Sn2
poor nucleophiles –> sn1
E1
tertiary best secondary okay weak base okay has NH or OH bond no stereochemistry requirements rate=k[substrate]
E2
all substrates okay strong base needed all solvents okay antiperiplanar geometry required --> β -elimination rate=k[substrate][base]
E1 and E2 reactions form
alkenes –> a base abstracts a proton for the carbon adjacent to the leaving group
one step elimination reaction
E2
two step elimination reaction
E1
Naming alcohols
begin with normal naming rules, but number with the side that reaches OH first
parent chain ends in anol
assign stereo chemistry –> if a chiral center is shown number this before the substituents
Alcohol reactivity
primary least –> tertiary most reactive
Boiling point increases in alkyls…
with larger groups ex: methyl has a lower boiling point than propyl
nucleophile
atom/ion with lone pairs used to form bonds –> lewis base –> anionic
N3
azide
OR
alkoxide
Rate of substitution with halides..
F is least reactant –> I is most reactant
Leaving group
group lost during nucleophile substitution or elimination –> usually halide
sn2 is
single step
sn1
multi step
inversion of configuration
nucleophile attacks from opposite of LG
backside attack
changes orientation
Sn2 substitution reactivity
tertiary is very slow --> methyl is fast most steric (most crowded) --> least crowded
Anion is most reactive in
neutral form (no charge)
nucleophilic trend across row
stronger base –> strong nucleophile
nucleophilic trend down group
larger atoms –> stronger nucleophile
Sn1 reactivity
methyl least reactive –> tertiary most reactive
x<12 carbons
cis
x>12 carbons
trans
stability of radicals
methyl least stable –> tertiary most stable
homolytic cleavage
bond breaking where each atoms retains a electron
F2
most reactive and exothermic
other halides
endothermic less reactive
LiALH4
reduces RCOOR (ester), RCOOH (carboxyl acids), RCOR (ketones) and RCHO (aldehydes)
R-CHO
aldehydes
R-CO-R
ketones
R-COOH
carboxyl acids
NaBH4
only reduces ketones and aldehydes
Grignard reagent
MgBr –> add to carbonyl (C=O) compounds,acts like an anion and attaches the C chain to the C=O and reduces the double bond while adding OH
1) BH3, THF –> 2) H2O2
hydroboration, OH goes to least substituted carbon and the double bond is reduced
free radical
an uncharged molecule (typically highly reactive and short-lived) having an unpaired valence electron
formal charge
valence electrons - sticks -dots
