Organic Chemistry 4 Flashcards
Define Hydrogenation
addition of H2 to a multiple bond
Hydrogenation
alkene to alkane
Notes on Hydrogenation
syn addition
H2/Pd, Pt, or Ni
Hydrogenation
How does heat affect stability?
less heat = more stable more heat = less stable
Syn Addition
two atoms or groups add to the same face of a double bond
Anti Addition
atoms or groups add to opposite faces of the double bond
Stereoselectivity
a reaction in which a single starting material can give two or more stereoisomeric products but yields one of them in greater amounts than the other
slowest to fastest rate of addition
HF«HI
weakest acid to strongest acid HI, HF, HCL, HBR
HF«HI
Markovnikov’s Rule
when an unsymmetrically substituted alkene reacts with a hydrogen halide, the hydrogen adds to the carbon that has the greater number o fhydrogesn, and the halogen adds to the carbon having fewer hydrogens
Name the mechanism and any rule that applies: CH3CH2CH=CH2 + HBR CH3CH2CH(BR)CH3
Hydrohalogenation and markovnikov’s rule
Define Hydrohalogenation
is the electrophilic addition of hydrohalic acids like hydrogen chloride or hydrogen bromide to alkenes to yield the corresponding haloalkanes
Hydrohalogenation
Alkene to alkyl halide Alkyne to Alkenyl Halide Alkyne to Geminal dihalide
Notes on Hydrohalogenation
Markovnikov’s Rule
Hydrogen Halide ex: HBR, HCL
Hydrohalogenation
Define Dehydration
loss of water
Dehydration
alcohol to alkene
What kind of mechanism does Dehydration take place
E1-carbocation E2-no carbocation
H2SO4 or H3PO4
Dehydration
Elimination 1
alcohol to alkene carbocation present H2SO4 or H3PO4 TERTIARY weak NU, weak base (NH3/CH3NH2/C5H5N or pyridine), heat SECONDARY heat, weak base, weak NU, good LG, steric hindrance
Elimination 2
alcohol to alkene no carbocation H2SO4 or H3PO4 PRIMARY strong bulky base sterically hindered SECONDARY strong base sterically hindered secondary LG
SN2
nucleophillic substitution chirality present=stereochem achiral present=no stereochem PRIMARY aprotic solvent,good NU,strong/weak base, unhindered SECONDARY aprotic solvent, good NU, unhindered, inversion, backside attack), no carbocation
SN1
carbocation forms enantiomers TERTIARY protic solvent, good NU, forms enantiomers SECONDARY protic solvent, good NU,
Very Good NU
I, HS, RS
Good NU
Br, OH, RO, CN, N3
fair NU
NH3, Cl, F, RCO2
Weak NU
H20, ROH
Very Weak NU
RCO2H
Aprotic Solvents examples
no hydrogen bonding; no acidic hydrogen; stabilize ions; favor SN2 EXAMPLES DCM, THF, ethyl acetate, acetone, DMF, MeCN or acetonitrile, DMSN or dimethyl sulfoxide,
Protic Solvents examples
hydrogen bonding; acidic hydrogen; cations and anions;favor SN1 EXAMPLES Formic acid, n-Butanol, isopropanol, ethanol, methanol, acetic acid, water
Primary
SN2 E2
Tertiary
SN1 E1
Secondary
all four
alkyl halide/AgNO3/aq. EtOH
SN1
Alkyl Halide/NaI/acetone
SN2
Alcohol/HX
SN1
alcohol/SOCl2 or PX3
SN2
alkyl halide/H2O
E1
alkyl halide/KOH/heat
E2
alcohol/H2SO4/heat
E1
Dehydrohalogenation
alkyl halide to alkene
What kind of mechanism is Dehydrohalogenation
E2
Strong Base
Dehydrohalogenation of E2
Free Radical Addition of HBR
Alkene to Alkyl Bromide
Notes on Free Radical Addition
Anti-Mark peroxides needed
HBR, Peroxides
Free Radical Addition of HBR
Hydration
Alkene to alcohol Alkyne to ketone
Notes on Hydration
Markovnikov’s
dilute H2SO4, H20
Hydration
Hydroboration-oxidation
Alkene to alcohol
Notes on Hydroboration-oxidation
Syn addition, anti-mark
1.B2H6, diglyme/2.H2O2, OH
Hydroboration-oxidation
Halogenation
Alkene to vicinal dihalide alkene to vicinal halohydrin alkyne to vicinal dihalide-trans alkene alkyne to tetrahalide
Notes on Halogenation
anti addition, OH adds to more substituted Carbon
X2, CHCL3, or CCl4
Halogenation
X2, H2O
Halogenation alkene to vicinal halohydrin
Epoxidation
Alkene to epoxide (carboxylic acid)
Notes on Epoxidation
Syn addition
peroxy acid
Epoxidation
Ozonolysis
Alkene to aldehydes or ketones alkyne to 2 carboxylic acids
Notes on Ozonolysis
Ozonide is intermediate
- O3/ 2. H2O, Zn or (CH3)2S
Ozonolysis
Formation of alkyl tosylate
alcohol to alkyl tosylate
Notes on alkyl tosylate
-OTs is leaving group
Tosylate chloride
Alkyl Tosylate
Formation of Alkyne Anion
Terminal Alkyne to Alkyne anion (conj. base) Na, NH3
NaNH2, NH3
Alkyne Anion
Alkylation
Alkyne anion to alkyne
Notes on Alkylation
Alkyne anion is LG
Methyl or primary alkyl halide
Alkylation
Formation of Alkyne
Vicinal dihalide to alkyne