Chapter 11: Alcohols and Thiols Flashcards
Why are alcohols slightly less acidic than water?
Because the conjugate base of an alcohol, and alkoxide, has a high electron density on the oxygen from the electron in the alkyl group, it is a weaker acid than water
Why are thiols far more acidic than alcohols?
Thiols are 5 orders of magnitude more acidic than alcohols because thiolate is a stronger more STABLE conjugate base due to polarizability of sulfur versus oxygen.
What are the polar effects on alcohol acidity?
Electronegative substituent groups enhance the acidity of an alcohol by pulling the electron density from the acidic proton of the OH group
Importance of polar effects increases as substituent gets closer to OH group
How do I get from an alkene to an alcohol?
Hydrating an alkene will get an alcohol. Pi electrons will attack proton on water to form carbocation on most substituted carbon, and a water will come in and attack the carbocation. It will for an OH group.
How do I get from an alcohol to an alkene?
Dehydration of an alcohol leads to an alkene. OH group attack a proton from H2SO4 and forms water which is a good leaving group. This forms a carbocation in which a base will come and attack a hydrogen on a beta carbon which will form a double bond.
What are the common abbreviations for sulfonate esters?
OMs = mesylate
OTs = tosylate
OTf = triflate
How do I get a sulfonate ester from an alcohol?
R-OMs,OTs, or OTf are great leaving groups.
Substitution: When a nucleophile attacks the carbon connected to one, the leaving group leaves and the R group remains on the nucleophile.
Elimination: When a nucleophile attacks a hydrogen on a beta carbon that pushes electrons to make a double bond that kicks off the OMs, OTs, OTf group
What is oxidation?
A transformation where electrons are lost
What is reduction?
A transformation where electrons are gained
How can a half-reaction be balanced?
Use H2O to add missing oxygen atoms
Add protons to balance missing H atoms
Add electrons to balance addition of H atoms
What reagent is used to convert secondary alcohols to ketones through an oxidative process?
Chromium-based reagents are used to convert an alcohol to a ketone
How does this process differ for primary alcohols?
For primary alcohols, there are two C-H bonds that can be oxidized, bringing the molecule to a carboxylic acid.
If PCC is used, the reaction is stunted at an aldehyde.
Why can’t tertiary alcohols be oxidized?
Because the carbon atom attached to the hydroxide does not have any hydrogen atoms, and so the double bond between carbon and oxygen can not be formed without the removal of a hydrogen to that carbon.
