Oxygen-Containing Compounds Flashcards
Physical properties of alcohols
- Hydrogen bonding.
- Higher boiling point than the same compound without the alcohol group.
- Water soluble as long as molecule does not contain a long hydrophobic region.
SN1 reaction with alcohols
SN2 reaction with alcohols
What factors favor SN1?
stable carbocation, tertiary carbon center, protic solvent.
What factors favor SN2?
unstable carbocation, primary carbon center, aprotic (but polar) solvent.
Describe the strength of the following oxidizing agents: KMnO4, CrO3, and PCC?
- KMnO4 and CrO3 will oxidize primary alcohols to carboxylic acids
- PCC (Pyridine Chlorochromate) and other weak oxidizing agents will only oxidize a primary alcohol to the aldehyde.
Secondary alcohols will always oxidize to what:
Ketones
Mechanism of Pinacol Rearrangement
A strong acid (H2SO4) protonates and then rearrangement occurs.
Protection of alcohol groups
Best protection group is trimseyl silyl:
- To protect, add Cl-SiMe3 to R-OH.
- The alcohol gets “capped” into R-O-SiMe3.
- To deprotect, add F-.
Reactions with SOCl2 and PBr3
R-OH + SOCl2 –> R-Cl (by products: SO2 + HCl)
R-OH + PBr3 –> R-Br (by products: H3PO3, R3PO3, HBr)
Preparation of mesylates, tosylates, and tosylates:
Purpose of preparing mesylates, tosylates, and triflates
They are great leaving groups for nucleophilic substitution
Esterification of alcohol
What is an inorganic ester?
replace the carbon of esters with a different atoms
Formation of inorganic ester using PBr3
Formation of an inorganic ester using SOCl2
Why are inorganic esters important for biochemistry?
In biochemistry DNA/RNA polymerization, the 3’-OH alcohol group attacks the 5’-phosphate to form an inorganic ester linkage (phosphodiester linkage of DNA/RNA backbone).
Hydrogen bonding of alcohols results in:
hydrogen bonding in alcohols give them a higher boiling point than their corresponding alkanes.
Effect of chain branching on physical properties of alcohols
going from straight chain to branched alkane (with same # carbons) = higher freezing/melting point, lower boiling point.
Physical properties of aldehydes and ketones
- C=O bond is polar, with the carbon partially positive and oxygen partially negative.
- Dipole-dipole interactions give these molecules higher boiling points than their corresponding alkanes, but not as high as the corresponding alcohols or carboxylic acids.
Nucleophilic addition at the carbonyl bond to form a hemiacetal or acetal.
Nucelophilic addition at the carbonyl to form an imine
Nucleophilic addition at the carbonyl to form an enamine
Halform reaction mechanism
Aldol condensation mechanism
Internal H-bonding in 1,3 di-carbonyls
Keto-Enol Tautomerism (extra: which is more stable?)
Formation of organometallic compounds and purpose of organometalic compounds
Organometallic compounds makes R-, which attacks C=O to make R-C-OH.
The purpose of organometallic compounds is to make carbon-carbon bonds.
Wolff-Kishner Reaction
Grignard Reagents for carbonyls
Grignard reagents are just like organometallic reagents, they produce R-.
Effect of substituents on reactivity of C=O
bulky groups on either side of C=O blocks access to the electrophilic carbon, so reactivity goes down.
Why are alpha protons acidic?
Alpha proton is acidic because the resulting carbanion is stabilized by resonance.
Physical properties and solubility of carboxylic acids
- High boiling point due to hydrogen bonding.
- Soluble in water.
Describe the general mechanism for a nucleophilic attack for a carboxylic attack.
What is the product of LiAlH4 and a carboxylic acid?
It creates a primary alcohol. Carboxylic acids can only be reduced by lithium aluminum hydride.
Decarboxylation mechanism for beta-keto acids
Reactants and mechanism for esterification
Carboxylic acid and R-OH in acidic conditions
Halogenation of Carboxylic Acids at the alpha position (four-step mechanism)
General principles of carboxylic acids
- High boiling points due to hydrogen bonding
- Dimerization due to hydrogen bonding
- Weak acid
Electron Withdrawing Groups Inductive Effect on Carboxylic Acids
electron withdrawing groups makes the acid stronger.
Physical properties of carboxylic acid derivatives
- C=O bond is polar, so there are dipole-dipole interactions.
- No hydrogen bond exists in acid chlorides, anhydrides, or esters unless there is an -OH group somewhere.
- Amides can hydrogen bond because of the N-H group. In fact, hydrogen bonding involving the amide backbone of polypeptides form the secondary structure of proteins.
- Amides have higher boiling points than the other acid derivatives.
- Acid derivatives have high boiling points than alkanes because of the C=O dipole interactions.
Synthesis of acyl chloride from carboxylic acid
Reactions of acyl chloride
Reactions of acid anhydrides
Reactions of esters
Amide to carboxylic acid
Reaction of carboxylic acids to acid derivatives
Nucleophilic substitution mechanism for carboxylic acids
Hoffman Rearrangement
Transesterification reaction
Hydrolysis of fats and glycerides (saponification)
Hydrolysis of amides
Relative reactivity of acid derivatives
Steric Effects on Carboxylic Acid Derivatives
bulky groups around the C=O group helps protect the carbon center from nucleophilic attack.
Strain of amides (beta-lactam)
Amides have a double bond characteristic between the carbon and nitrogen. This means that the C-N bond can not rotate.
An example is beta-lactam, which is a four-membered ring with 1 amide in it.
