CH 220C Reduction

9-Fluorenone MSDS

Moderate FH PC NM

Methanol MSDS

Severe FH NC PM

Sodium borohydride MSDS

Moderate FH NC NM

Sulfuric acid solution MSDS

Combustible KC NM

9-Fluorenol MSDS

Moderate FH PC NM

Why are catalytic reductions preferred experimentally?

produces very little waste

Why are we not doing a catalytic reduction?

hydrogen gas is very flammable

Reductions can involve an increase in the electron density at a carbon atom because:

the bond between carbon and an electronegative atom has been replaced with a carbon-hydrogen bond

Reductions are also:

reactions where new carbon-hydrogen bonds are formed by adding hydrogens to functional groups

Reductions result in a ___ in the oxidation number of a carbon atom

decrease

1 mol NaBH4 reduces __ mols of ketones

4

Why do we use NaBH4?

Most selective due to low electronegativity difference with hydrogen

Why can NaBH4 be used in solvents like methanol?

Boron is small, more electronegative, and less reactive

Why do hydride reductions avoid protic solvents?

Reducing agent will react with any protons available to produce hydrogen gas

How do hydride reductions work?

selective reduction of functional groups susceptible to nucleophilic attack by hydride ion

Carbon-carbon double bonds are ___ susceptible to ___, whereas carbon-oxygen and carbon-nitrogen double bonds ___

are not, nucleophilic attack, are

What does NaBH4 NOT reduce?

Esters

What are we looking for in the IR?

disappearance of carbonyl peak, extremely weak OH peak

Why do solid alcohols have less signal strength than liquid alcohols?

solids have less hydrogen bonding than liquids

What does a large hump in the IR indicate?

presence of water

Why should the lid be screwed on for NaBH4?

It will absorb protons from the air

What is the purpose of the reflux?

To prevent product from evaporating

Why do we boil the mixture?

To release the alcohol from the product

Why do we rinse the reflux product with deionized water?

to neutralize it

What is the purpose of the recrystallization step?

get rid of impurities

When is the reflux finished?

when the liquid is clear

When should heat be lowered to 150C?

vapor line is 1/3 of the way

How much 9-fluorenone in methanol?

3 mL 0.185M

How much sodium borohydride?

7 drops 4.4M

How much sulfuric acid?

0.45 mL 3M

9-fluorenol melting point

152-158

If product does not fully dissolve?

Add methanol in 0.5 mL increments