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MCAT chem > Organic Chem reactions / reagents > Flashcards

Organic Chem reactions / reagents Flashcards

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1
Q

reagent to oxidize a primary alcohol to an aldehyde?

A

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

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2
Q

reagent to oxidize a secondary alcohol to a ketone?

A

jones reagent or chromium reagents such as Na2Cr2O7

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3
Q

What does NaBH4 do?

A

reduces ketones / aldehydes to alcohols

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4
Q

what does LAH (LiAlH4) do?

A

reduces carboxylic acids to alcohols

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5
Q

R-Br + Mg forms?

A

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.

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6
Q

NaCN reacting with a ketone yields?

A

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

called a cyanohydrin

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7
Q

Reacting an aldehyde with R-NH2 and acid makes?

A

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

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8
Q

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

A

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

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9
Q

what is decarboxylation?

A

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

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10
Q

Acid catalyzed esterification? (Fischer esterification)

A

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

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11
Q

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

A

C triple bond N converts to a carboxylic acid

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12
Q

What reaction is this?

NH4Cl and NaCN are added to an aldehyde

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

A

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

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13
Q

What reaction is this?

NH4Cl and NaCN are added to an aldehyde

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

A

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

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14
Q

what is the enolate anion?

A

a deprotonated carbonyl species which exhibits resonance.

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15
Q

What is Keto-Enol tautomerism? which is more stable

A

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

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16
Q

what are mesylates and tosylates?

A

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.

17
Q

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

A

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

18
Q

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

A

LDA - kinetic product
NaOH - thermo product

cold temperature also promotes kinetic product.

19
Q

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

A

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

20
Q

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.

A

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

21
Q

what is a nucleophilic addition - elimination reaction?

A

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)

22
Q

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

A

an ester

R-CO2H + R-OH —> RC(=O) - OR

23
Q

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

A

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)

24
Q

Saponification produces what?

A

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

25
Q

saponification of triglycerides yields?

A

glycerol and fatty acids

26
Q

treating a carboxylic acid with SOCl2?

A

makes an acyl chloride

27
Q

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

A

true!

28
Q

what is the reactivity of carboxylic acid derivatives

A

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)

29
Q

Reacting Acyl chloride with NHR2 yields?

A

a tertiary amide

CH3-C(=O) - NR2

30
Q

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

A

up

31
Q

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

A

true

32
Q

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

A

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

33
Q

what is a reducing sugar?

A

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

34
Q

what is beneficts test?

A

distinguishes between reducing sugars and non-reducing sugars

35
Q

will a hemi-acetal produce a positive benedict test?

A

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!!

36
Q

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

A

true

MCAT chem (11 decks)

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