Organic Chem reactions / reagents

Question 1

reagent to oxidize a primary alcohol to an aldehyde?

Answer 1

PCC, all other oxidizing agents will go to carboxylic acid;

Question 2

reagent to oxidize a secondary alcohol to a ketone?

Answer 2

jones reagent or chromium reagents such as Na2Cr2O7

Question 3

What does NaBH4 do?

Answer 3

reduces ketones / aldehydes to alcohols

Question 4

what does LAH (LiAlH4) do?

Answer 4

reduces carboxylic acids to alcohols

Question 5

R-Br + Mg forms?

Answer 5

R-Mg-Br = Grignard reagent which is a powerful nucleophile. these attack carbonyl centres and add alkyl groups. Acid work up is required to protonate the oxygen.

Question 6

NaCN reacting with a ketone yields?

Answer 6

addition of the CN group and protonation via an acid to get an OH group.

called a cyanohydrin

Question 7

Reacting an aldehyde with R-NH2 and acid makes?

Answer 7

an imine which is a carbon double bonded to a nitrogen which has some R group attached to it.

Question 8

Reacting an aldehyde / ketone with R-NH2 and acid makes?

Answer 8

an imine which is a carbon double bonded to a nitrogen which has some R group attached to it.

note: primary amine must attack

if a secondary amine attacks we get an enamine which is a C=C-NR2 group

Question 9

what is decarboxylation?

Answer 9

add heat to a compound with a carboxylic acid and CO2 will be kicked off

Question 10

Acid catalyzed esterification? (Fischer esterification)

Answer 10

reacting a carboxylic acid with acid and alcohol to create an ester

CO2H + H+ primes the carboxylic acid

then CO2H2 is attached by R-OH and the H deprotonates after

Question 11

What occurs when you have a C triple bonded to an N and you add H3O+ (Acid)

Answer 11

C triple bond N converts to a carboxylic acid

Question 12

What reaction is this?

NH4Cl and NaCN are added to an aldehyde

this is followed by the addition of H3O+ to form ____?

Answer 12

Strecker synthesis which forms amino acids. The R group attached to the initial aldehyde determines the amino acid.

Question 13

What reaction is this?

NH4Cl and NaCN are added to an aldehyde

this is followed by the addition of H3O+ to form ____?

Answer 13

Strecker synthesis which forms amino acids. The R group attached to the initial aldehyde determines the amino acid.

Question 14

what is the enolate anion?

Answer 14

a deprotonated carbonyl species which exhibits resonance.

Question 15

What is Keto-Enol tautomerism? which is more stable

Answer 15

when enolates are formed, the electrons can form a carbon = carbon double bond and shift the carbonyl double bond away to form an alcohol. (Enol). The double bond C = O can reform and break the C=C bond to form a ketone (keto)

keto is more stable

Question 16

what are mesylates and tosylates?

Answer 16

They replace the H on OH groups and make alcohols inert in reactions. They are also great leaving groups. Note addition of the TsCl or MsCl retains stereo but Sn2 after inverts it.

Question 17

what occurs if a strong base deprotonates the alpha hydrogen of an imine?

Answer 17

the electrons shift to break the imine C=N bond and rather form an enamine.

Question 18

LDA vs. NaOH in the de-protonation of the alpha hydrogen in aldol reactions?

Answer 18

LDA - kinetic product
NaOH - thermo product

cold temperature also promotes kinetic product.

Question 19

If you see a reaction where it shows an aldol condensation product with (-H2O) what comes next?

Answer 19

dehydration reaction in which the OH group is removed and a C=C bond is made (this occurs with heat and acid)

Question 20

T or f, in nucleophilic addition reactions a pi bond breaks and two sigma bonds are made. A elimination reaction shows 2 sigma bonds break while a new pi bond is made.

Answer 20

true! a nucleophilic substitution would show the addition of one sigma and the loss of another.

Question 21

what is a nucleophilic addition - elimination reaction?

Answer 21

when a nucleophile attacks a carbonyl species and breaks the C=O pi bond. Then reformation of the pi bond kicks off the most appropriate LG. Similar to substitution but in two steps. (Sn1 is 2 steps but different mechanism)

Question 22

What is made when a carboxylic acid reacts with an alcohol and acid?

Answer 22

an ester

R-CO2H + R-OH —> RC(=O) - OR

Question 23

hydrolysis of esters: adding acid to an ester makes? What about reacting an ester with another ester in acid?

Answer 23

carboxylic acid forms if you expose an ester to H3O+

if you expose an ester to acid in the presence of another ester, the ester will attack the protonated ester and cause transesterification (the ester group changes it’s R group)

Question 24

Saponification produces what?

Answer 24

base catalyzed ester hydrolysis which creates carboxylate anion. You must protonate it to form the carboxylic acid.

Question 25

saponification of triglycerides yields?

Answer 25

glycerol and fatty acids

Question 26

treating a carboxylic acid with SOCl2?

Answer 26

makes an acyl chloride

Question 27

T or f, carboxylic acids can be made from any carboxylic acid derivative (acyl chloride, ester, amide, etc.) by heating it in acid (aq) solution

Answer 27

true!

Question 28

what is the reactivity of carboxylic acid derivatives

Answer 28

acyl chlorides > anhydrides > esters > amides

you can make anything on the left using the stuff on the right but not vice versa (can’t make anhydride from amide)

Question 29

Reacting Acyl chloride with NHR2 yields?

Answer 29

a tertiary amide

CH3-C(=O) - NR2

Question 30

in B-D-glucose is the anomeric hydroxyl group up or down?

Answer 30

up

Question 31

t or f, the anomeric carbon is the carbon with the C=O bond in the open chain form?

Answer 31

true

Question 32

t or f, mammalian enzymes cannot hydrolyze beta-glycosidic linkages

Answer 32

true and false, this is true despite one exception –> lactase can metabolize lactose for many people

Question 33

what is a reducing sugar?

Answer 33

Any carbohydrate which can act as a reducing agent due to a free aldehyde or free ketone group.

Question 34

what is beneficts test?

Answer 34

distinguishes between reducing sugars and non-reducing sugars

Question 35

will a hemi-acetal produce a positive benedict test?

Answer 35

yes, hemi-acetals are in equilobrium with open chain sugars. Therefore, their free aldehyde and ketone group will react with benedicts reagent to give a positive test.

Note: once the sugar is in a glycosidic linkage (acetal form) it will not!!

Question 36

all aldehydes, ketones, and hemi-acetals give positve benedict test results.

Answer 36

true