What can primary alcohols be oxidized to?
2
Aldehydes or Carboxylic acids
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| Term | Definition |
|---|---|
What can primary alcohols be oxidized to?
2 | Aldehydes or Carboxylic acids |
What can secondary alcohols be oxidized to? | Ketones |
What can tertiary compounds be oxidized to? Why? | - Tertiary compounds cannot be oxidized to C=O
- there are no H's to take |
What are the solvents involved in the PCC oxidation?
2 | - PCC
- CH2Cl2 or DCM |
Does the PCC oxidation happen under aqueous or anhydrous (no water) conditions? | Anhydrous |
What are primary alcohols converted to during the PCC oxidation? | Aldehydes |
What are secondary alcohols converted to during the PCC oxidation? | Ketones |
T/F: the solvent participates in the reaction | False |
What are the solvents involved in the Jones oxidation?
2 | - H2CrO4
- H2O/Acetone |
Does the Jones oxidation happen under aqueous or anhydrous conditions? | Aqueous |
What are primary alcohols converted to during the Jones oxidation? | Carboxylic acids |
What are secondary alcohols converted to during the Jones oxidation? | Ketones |
What solvents are involved during the Swern oxidation? | - DMSO, (COCl)2
- NEt3 |
Does the Swern oxidation happen under aqueous or anhydrous conditions? | Anhydrous |
What are primary alcohols converted to during the Swern oxidation? | Aldehydes |
What are secondary alcohols converted to during the Swern oxidation? | Ketones |
What hybridization are all carbonyl functional groups? What are their bond angles and geometry? | Sp2
- 120 degrees, trigonal planar |
If the C=O bond is polarized, is it electrophilic at the C or the O? | Electrophilic at the C |
Which undergo nucleophilic addn faster: aldehydes or ketones? Why | - Aldehydes
- Due to steric and electronic factors |
What are steric and electronic factors? | Steric: Aldehydes only have one alkyl group = less sterically congested
Electronic: Aldehydes are more electrophilic because it is only stabilized by one EDG (alkyl group) |
What happens when a carbonyl is attacked by a Nu? What happens to hybridization? | The weakest bond (DB) breaks = tetrahedral intermediate
- Sp2 to Sp3 |
What happens under basic conditions during a nucleophilic attack?
2 | - Nu directly attacks carbonyl carbon
- Protonates after w/ H-A (acidic workup) |
What happens under acidic conditions during a nucleophilic attack?
3 | - Carbonyl first protonated to make it more electrophilic
- Nu-H attacks carbonyl carbon
- A- takes H from Nu-H |
Why can Nu attack create steroisomer? | Because you can attack from either face of the DB |
Why do you need to remove moisture and oxygen during organometallic rxns? | Radical intermediates can form side-products |
Which bears more electron density in the C-M bond? Why | - C
- C has a higher electronegativity |
T/F: acidic protons can be present during organometallic rxns | False, all organometallic reagents are BASIC and nucleophilic |
How can carbonyl compounds be converted to alcohols by reduction? | Using metal hydrides under BASIC conditions |
What does sodium borohydride reduce?
2 | Aldehydes and Ketones |
What solvents does NaBH4 use? | Protic solvents
- MeOH, EtOH |
What does lithium aluminium hydride reduce?
5 | - Aldehydes
- Ketones
- Esters
- Amides
- Nitriles |
What solvents does LiAlH4 use? | Aprotic solvents
- THF, Et2O |
Which is more reactive: LiAlH4 or NaBH4 | LiAlH4 |
What step is always requires no matter what hydride you use? | Acidic workup to quench (stop) rxn |
T/F: 0.5 eq of NaBH4 (or LAH) can reduce 1 eq of ketone | False
- 0.25 eq of NaBH4 (or LAH) can reduce 1 eq of ketone
- All 4 hydride anions are transferred to electrophiles |
What forms when aldehydes/ketones react w/ water under acidic or basic conditions? | Hydrates |
Describe what a hydrate looks like | Two hydroxyl groups (OH) attached to same sp3 carbon |
Is the synthesis of a hydrate reversible or irreversible? | Reversible |
What can you do to push the hydrate synthesis rxn forward or backward? | Forward: add excess H2O = hydrate
Backward: remove water using drying agent = carbonyl |
Do EDG favour or disfavour hydrate formation? Why? | - Disfavour
- Because the carbonyl carbon is less electrophilic/reactive |
Is the Keq for hydrate formation lower for aldehydes or ketones? | Low Keq for ketones |
Do EWG favour or disfavour hydrate formation? Why? | - Favour
- Carbonyl carbon is more electrophilic/reactive |
Is the Keq higher for EDG or EWG? | Higher for EWG |
What solvents are used to convert ketones/aldehydes to hydrates?
2 | - H2O
- H+/OH- |
What solvents are used to convert ketones/aldehydes to acetals?
2 | - Two eq's of an alcohol (ROH)
- H+ |
What always forms during acetal formation? Describe what it looks like | Intermediate: Hemiacetal
- 1 hydroxyl (OH) group and one alkoxy (OR) group attached to sp3 carbon |
Can acetal formation occur under basic conditions? Why? | - No, only under acidic conditions
- Acid needs to protonate both the carbonyl O and many LG's to create the loss of water |
Does acetal formation favour aldehydes or ketones as SM? | Aldehydes |
Is acetal formation reversible or irreversible? | Reversible |
What would you use to hydrolyze an acetal?
2 | - Acid
- Excess H2O |
When do you get cyclic acetals? | When both eq's of alcohol are tethered together |
Are cyclic acetals more or less stable then acyclic ones? | More stable, harder to hydrolyze |
Which reactions occur faster: Intramolecular or Intermolecular? | Intramolecular (cyclic) |
What is a protecting group? | Group that is added to prevent a rxn from going |
Acetals can protect what functional groups?
3
| - Aldehydes
- Ketones
- Alcohols |
What are dithianes? | Cyclic thioacetals |
Are thioacetals more or less stable than standard acetals? | More |
What solvents do you need to convert ketone/aldehyde to dithiane?
2 | - 2 eq's of SH tethered together
- Lewis acid (ex. BF3) |
What reagents can be used to deprotect the reaction?
3 | - Mercury, salts
- Oxidation of S to sulfoxides
- Rxn of S atoms w/ good electrophile (ex. MeI, NBS) |
How can you completely reduce a thioacetal? | Raney Nickel |
Do the most simple carbs have an aldehyde or ketone group? | Aldehyde |
What type of molecule do monosaccharides exist as? | Cyclic due to hemiacetal formation |
Acetal formation can generate 2 diff isomers at the _____ carbon to create _______ | - Anomeric carbon
- Alpha and beta anomers |
What happens when ketones/aldehydes are treated w/ primary alcohols or ammonia? | Imine formation |
What is always formed during imine formation? Describe what it looks like | Hemiaminal
- 1 hydroxy group (OH) and 1 NHR group |
What solvents are used during imine formation?
2 | - RNH2
- H+ |
Are acyclic imines stable or unstable? | Unstable
- Will hydrolyze easily in presence of aq acid to reform C=O |
What must be removed during imine formation to drive the rxn forward? | Water |
What isomer is most stable in imine formation? | One with largest R groups TRANS to eachother |
What happens when you are using a secondary amine and the iminium ion is formed? | There is no proton to remove from charged N atom = proton next to iminium ion (alpha position) is removed = enamine |
Which molecules react with carbonyls to generate stable imines? | - Hydroxylamine
- Hydrazine
- Semicarbazides |
Describe the structure of an imine | Heteroatoms whose LP's are conjugated to the DB |
What does the resonance form of the imine product look like? | Neg charge on imine carbon = not susceptible to Nu attack |
What solvents are used during the Wolf-Kishner reduction? | KOH, Heat |
What steps are reversible and irriversible during wolf-kishner reduction? Why? | - Reversible: hydrazone formation
- Irreversible: final reduction step due to loss of N2 gas |
What are the 3 ways to reduce a C=O to a -CH2- group? | - Wolf Kishner
- Clemmensen
- Desulfurization |
What is the purpose of the Wittig rxn? | Convert aldehydes/ketones to alkenes |
Which isomer is favoured in the Wittig rxn? | Z isomer |