Allt Flashcards
What is a Gringard reagent?
A magnesium atom added to an alkyl halide, the Mg will insert in between the carbon and halogen. These are great nucleophiles and will react (basic) even with very weak acids.
Draw the base structure of a ketone.
See book
Draw the base structure of an aldehyde.
see book
Why do aldehydes and ketones undergo only nucleophilic addition reactions?
The aldehydes and ketones are attached to a group that is too strong of a base to be eliminated from the compound.
What is the product of a nucleophilic addition of a Grignard reagent with methanal (formaldehyde)? Draw the mechanism.
A primary alcohol
What is the product of a nucleophilic addition of a Grignard reagent with an aldehyde other than methanal? Draw the mechanism.
A secondary alcohol
What is the product of a nucleophilic addition of a Grignard reagent with a ketone? Draw the mechanism.
A tertiary alcohol
What determines a good leaving group of an alkyl halide in a SN2 reaction?
Weak bases. Weak bases are stable bases since they don’t share their electrons (they would’ve shared with the proton) easily. Therefore the base is not strongly bonded to the carbon.
What makes a good nucleophile in a SN2 reaction?
The stronger the base, the better the nucleophile. Stronger bases have the negative charge on less electronegative atoms (the electrons are not pulled as strongly towards the negative atom, shares their electrons more easily with protons)
What makes a weak base (electronegativity)?
Weak bases are strong acids and have their negative charge on a more electronegative atom.
What is the rate mainly controlled by in a Sn2 mechanism?
Steric hindrance - nucleophiles with bulky structures cannot easily approach the backside of the carbon, which slows down the rate.
What is the rate mainly controlled by in a Sn1 mechanism?
The stability of the carbocation; tertiary carbocations form more easily than secondary and primary (because of better stability) which affects the rate of the reaction.
What does a unimolecular rate-determining step mean? Sn1 or SN2 reaction?
Only one molecule is involved in the rate determining step. SN1 reaction.
What does a bimolecular rate-determining step mean? Sn1 or SN2 reaction?
Two molecules are involved in the rate determining step. SN2 reaction.
How does the nucleophile affect the rate of a SN2 reaction and why?
A better nucleophile is a strong base and therefore shares their electrons more easily with other compounds.
How does the nucleophile affect the rate of a SN2 reaction and why?
A better nucleophile is a stronger base (less electronegative) and therefore has a better distribution of electrons, and thus more easily shares their electrons with other compounds.
By what mechanism does pyran and furan rings form?
Formation of hemiacetals and hemiketals is the reaction between an alcohol and an aldehyde/ketone. If the reacting groups belong to the same molecule, then a ring structure can form.
By what mechanism does O-glycosidic bonds between monosaccharides form?
Acetal and ketal formation: The hemiacetal/hemiketal of one monosaccharide reacts in a condensation reaction with the hydroxide group of another monosaccharide and forms an O-glycosidic bond.
In the second electrophilic addition in the addition of hydrogen halide to an alkyne, what is the product?
An alkane.
What is the product of the electrophilic addition of a hydrogen halide to an alkyne?
An alkene.
What type of products form in the addition of H+ to an internal alkyne?
It forms two type of products of equal amount, because the hydrogen kan with equal ease attach to either one of the sp carbons. (both are attached to R groups instead av hydrogens).
