organometallics/alcohols, diols, thiols Flashcards
What are organometallics?
Compounds containing a carbon-metal bond
What is the relative electronegativity in organometallics?
C is more electronegative than metal
Why are organometallic important in reactions?
They form new C-C bonds, strong bases
What type of bond is in an organometallic?
Polar, covalent bond
What are carbanions?
Negatively charged C that are highly nucleophile
What are the 7 options that a metal can be in an organometallic compound?
Mg, Li, Zn, Cu, Na, K, Al
Why cant you have water in grignard reactions?
It will protonate the organometallic making it useless in the reaction
What is the general equation for organometallics?
R-M + R’OH -> R-H + M + OR’
What are two important organometallics? What is their reactivity?
R-Li organolithium (alkyl lithium)-more reactive
R-MgX grignard-less reactive
What are the conditions to prepare organolithium?
Reactants: R-X + 2Li
Solvent: ether, 0ºC
Product: R-Li + LiX
What halogens can be used in preparation of organolithium ( R-Li ) 3?
I, Br, Cl
What is the process of preparation of grignard?
Reactants: R-X
Solvent: Mg, ether or THF
Product: R-MgX
What can the R groups be in preparation of R-Li and R-MgX (3)?
Alkyl, alkenyl, and aryl
What is the product when grignards react with carbonyls?
Alcohol is produced
What type of alcohol is produced when grignard reacts with aldehydes or ketones? Does the same rule apply to organolithiums?
Aldehydes: 1º or 2º
Ketones: 3º
Same rules apply to organolithiums
What are organocuprates?
R2CuLi
What are the possible R groups in organocuprates (3)?
Alkyl, alkenyl, Aryl
What the three possible X atoms used in organocuprates? Which is the most common?
Cl, Br, I (most common)
What is the purpose of using organocuprates in synthesis?
Produce new R-R bonds
What are the conditions of going from an alkyl halide to alkyl using organocuprates?
Reactant: R-X
Conditions: R2CuLi, ether
Product: R-R’
What are two important steps in the mechanism of organocuprates?
Oxidative addition and reductive elimination
How do you produce a cyclopropane via Simmons Smith reaction? What are the conditions?
Reactant: alkene
Conditions: ICh2I, Zn(Cu) ether
Product: cyclopropane
What is the benefit to using R-ZnX compared to grignard?
Less reactive
What are the four types of palladium catalyzed cross coupling?
Stille, Suzuki, Negishi, Heck
What type of organic compounds are used in the four palladium catalyzed cross coupling reactions?
Stille- organotin
Suzuki- organoboron
Negishi- organozinc
Heck- alkene
What occurs in palladium catalyzed cross coupling reactions?
C with the special atom (Zn, Sn, B, C=C) will bond to the C with the halogen on the other reactant
What is oxidation in organic chemistry?
Removal of H2
What is reduction in organic chemistry?
Addition of H2
What conditions are used to reduce aldehydes and ketones? What does it reduce?
H2, Pt (Pd, Ni, Ru) in ethanol. Reduced both C=O and C=C
What compound do you use when you want to reduce the C=O but not the C=C?
Sodium borohydride. It delivers a hydride (H-) to the carbonyl group
What is LAH? What is the benefit of using it? Dangers?
Lithium Aluminim Hydride, more reactive than NaBH4 but also delivers hydride to C=O. Must be carried out in cold conditions and reacts violently with H2O and ROH
Can you replace any H in the sodium borohydride or LAH for duterium and get it in your product?
Yes, unless the deuterium is in CD3OH position in the ethanol solvent
What are the conditions of carboxylic acid and ester reduction with LAH?
Reactant: carboxylic acid or ester
Conditions: 1. LAH, ether 2. H2O
Product: primary alcohol
What are the conditions in grignard addition to epoxides?
Reactant: R-MgBr + epoxide
Conditions: 1. Ether 2. H3O+
Product: primary alcohol
What are diols?
Molecules with 2 vicinal OH groups
What occurs in hydroxylation? What are the conditions?
Reactant: alkene
Conditions: OsO4 (osmium tetroxide), tBuOH, tBuOOH, -OH
Product: diol
What is the key intermediate in hydroxylation?
Osmate ester. When the O’s are added to the same face from the osmium tetroxide
What are the reaction conditions of sulfonate esters?
Reactant: alcohol
Conditions: TsCl, pyridine
Product: Tazolate (OTs) group instead of OH
Can tertiary alcohols be oxidized? Why or why not?
No, there is no H to pull off of the C that is bound to OH.
What is the oxidizing agent in potassium dichromate? How does it get to this point?
K2Cr2O7. Chromic acid is the oxidizing agent after H2SO4 and H2O act on potassium dichromate
Why does primary alcohol oxidation result in carboxylic acid instead of aldehyde?
Aldehydes are hydrated under acidic aq solutions which is used in oxidation so it goes straight to carboxylic acid
How do you form an aldehyde from a primary alcohol?
Use anhydrous conditions. PCC and CH2Cl2
What are three other oxidizing agents that act the same as potassium dichromate?
Na2Cr2O7, H2SO4, H2O
H2CrO4
CrO3, H3O+
What are thiols?
Alcohols but oxygen is a sulfur RSH
What occurs in esterification? What are the conditions?
Condensation occurs
Reactant: alcohol + carboxylic acid, anhydride, acid chloride
Conditions: H+ (catalytic) or pyridine
Product: Ester
Reaction conditions to go from ester to primary alcohol?
- LAH, ether 2. H2O
Reaction conditions to go from primary alcohol to carboxylic acids?
K2Cr2O7, H2SO4, H2O or other chromic acid reagents
Reaction conditions to go from primary alcohol to aldehyde?
PCC, CH2Cl2. Must be anhydrous conditions!
Reaction conditions to go from aldehyde to carboxylic acid?
K2Cr2O7, H2SO4, H2O
Reaction conditions of reduction of carboxylic acid to primary alcohol?
- LAH, ether 2. H2O
Reaction conditions of aldehyde to primary alcohol reduction?
NaBH4, CH3OH or 1. LAH, ether 2. H2O or H2, Pt
Reaction conditions of oxidation of secondary alcohol to ketone?
K2Cr2O7, H2SO4, H2O or PCC, CH2Cl2 or chromium reagent
Reaction conditions of ketone to secondary alcohol reduction (3)?
NaBH4, CH3OH or 1. LAH, ether 2. H2O or H2, Pt
What are 5 ways to form alcohols?
- Hydration of alkene (H2SO4, H2O)
- Hydroboration Oxidation on alkene (1. B2H6 2. NaOH, H2O, H2O2)
- Halohydrin formation of alkene (Br2, H2O)
- Grignard reduction of carbonyl based group (1. RMgBr, ether 2. H3O+)
- Organolithium reduction of carbonyl based group (1. RLi, ether 2. H3O+)
What is the benefit of using H2, Pt in reductions? What about NaBH4 and LAH?
H2, Pt reduce both the C=O and C=C
NaBH4, CH3OH reduces ONLY C=O
LAH, ether, H2O reduces ONLY C=O
Reaction conditions for forming thiols?
Reactant: alkyl halide
Conditions: NaSH(R), -S (Sn2) reaction
Product: thiol, S replaces halide ion
What are three reactions of alcohols? Conditions and substitution?
- Hydrogen halide (ROH2/3º) H-Br
- PBR3 or SOCl2 (ROH methyl, 1,2º)
- Dehydration (zaitsevs rule) H2SO4 or H3PO4 and heat
