Final Exam Flashcards
list 3 IMF weakest to strongest
LD, DD, hbond
as IMF strength increases, what happens to BP?
also increases
in analagous molecules, which has a high BP: alcohol or amine?
alcohol always
list classes of amines in increasing to decreasing BP
priamry higher than secondary higher than tertiary
when are amines soluble in water?
when contain 5 or fewer carbons per amino group
which is the stronger base: amines? or alcohols and ethers?
amines generally stronger bases than alcohols and ethers
localized or DL LP for better base?
localized
more or less electron density for a better base?
more
EDG or EWG for better base?
EDG
give the 3 types of electron donating groups
lone pair conjugated outside benzene; lone pair with res outside benzene, and alkyl groups; all ortho/para
give the 3 types of EWG groups
halogens (O/P), pi bonds conjugated outside the ring (like CN), are meta, and positive nitrogen or carbon attach to hella electronegative outside the ring, also meta
describe how aromaticity plays into basicity
if LP is what makes a molecule aromatic, it aint a good base; if non or antiaromatic in the first palce, less stable and better base
what are the 2 ways to make an amine from alykl halide?
- nitrile (CN) method (adds a carbon)
- azide (1. NaN3 2. LAH 3. H2O) method (not add carbon)
both SN2 so work great on methyl and primary halides, work ok on secondary, but no work on tertiary halides
how to make amine from carboxylic acid?
turn to acid chloride with SOCl2, then make amide with xs NH3, then reduce and remove C=O double bond with 1) LAH 2) H2O
how to make amines from benzenes or benzene derivatives?
use HNO3 and H2SO4 to make NO2 (keep in mind directing effects of any existing benzene groups) then use H2, Pt to reduce or the milder 1) metal (Fe, Zn, Sn, SnCl2), H3O+ 2) NaOH to not reduce any other groups too
why can’t use ammonia to make primary amine?
overalkylation occurs; will keep going until no lone pairs left and now have a quarternary ammonium salt
what 4 things need for reductive amination?
- carbonyl (aldehyde or ketone)
- acid
- nitrogen source
- NaBH3CN
what can be used to make secondary and tertiary amines?
reductive amination
why is NaBH3CN used in reductive amination instead of NaBH4?
the CN stabilizes boron and makes mroe selectively reductive; can use one pot apporach to reduce imine that forms between carbonyl and nitrogen source without reducing carbonly before reaction even starts
what is a substitution method to make primary amines without overalkylation without needing a carbonyl?
gabriel synthesis
what need for Gabriel synthesis?
- phtalamide
- KOH
- alkyl halide (pirmary or secondary, no tertiary)
- hydrazine (H2NNH2) to free amine
how do you make an aryldiazonium salt?
take an aniline and add NaNO2 plus HCl
what is an aryl diazonium salt?
a GREAT electrophile with a fantastic leaving group
what 5 subsequent reactions can be perfomed from turning an aniline into an aryldiazonium salt?
- CuX (X= Br, Cl, I, CN) to put X on benzene
- HBF4 to put F on benzene
- H3PO4 to put H on benzene
- H3O+ and heat to put OH on benzene
- combine with a benzene nucleophile to make an azo dye
what is the electrophile in an azo dye?
the aryldiazonium salt
what is the nucleophile in an azo dye?
the most activated, or least deactivated ring
what does the diazonium salt derive from in an azo dye?
aniline
how do you take an aniline to a diazonium salt?
- NaNO2, HCl (to form aryldiazonium)
2. add nucelophilic ring
what makes an L amino acid?
NH3 group on the left in a fischer projection
what happens in pH = pKa?
equal amounts of protonated and deprotonated forms exist
what happens in pH is greater than pKa?
then solution is basic relative to amino acid and deprotonated forms exist predominantly
what happens when pH is less than pKa?
then solution is acidic relative to amino acid and mostly protonated forms exist
what is the deprotonated form of the amine group of an amino acid?
NH2, no charge
what is the deprotonated form of the carboxylic in an amino acid?
COO-, negatively charged
what is the protonated form of the amino group of an amino acid?
NH3+, positively charged
what is the protonated from of the carboxylic acid in an amino acid
COOH, no charge
what is a zwitterion?
a net neutral compound that exhibits charge separation (both positive and negative bits within)
what can a zwitterion act as? what does this make it called?
both acid and base, amphoteric
what 2 characteristics are high in a zwitterion?
high melting point and high solubility in water
what is the isoelectric point? (pI)
the point where the zwitterion is at its maximum concentration
what are the 2 ways to calculate pI?
- if amino acid does not have a side chain with a pKa value, pI is the average of the amine and carboxyylic acid pKa values
- if amino acid DOES have a side chain with a pKa value, then the pI is the average of the two most similar values
what is electrophoresis?
separation utulizing differences in pI values
what is electrophoresis helpful for?
determining what amino acids are present in a mixture
describe the set up for electrophoresis
buffer solution between a positively charged electrode (anode, attracts ANions or negatively charged) and negatively charge electrode (cathode, attracts plussy CATions)
what happens in electrophoresis if the buffer solution pH is lower than the pI of the amino acids it contains?
then amino acids exist in protonated forms and migrate toward cathode (negative electrode)
what happens in electrophoresis if the buffer solution pH is higher than the pI of the amino acids it contains?
then amino acids exist in deprotonated forms and migrate toward the anode (positive electrode)
what happens as the difference between pH and pI increase?
the molecules move faster toward their respective anodes
which moves faster in electrophoresis: larger or smaller molecules?
larger molecules move faster
what happens in electrophoresis if the solution pH is equal to the pI of the amino acids it contains?
amino acids will not move; stay in middle
how are amino acids connected together?
through peptide bonds (amide bonds/linkages) from N terminus to C terminus
what kind of reaction joins amino acids? what does this mean?
condensation reaction; joins molecules together and emits a small byproduct (H2O in this case)
describe the condesation reaction that brings amino acids together
the N of one amine group reacts with the carbonyl carbon of the other amino acid, losing H2O in the process
if the R group is on top of the back bone, what stereochemistry will it be given?
a wedge
if the R group is on the bottom of the backbone, what stereochemistry will it be given?
a dash
when predicting the charge of a polypeptide at a given pH what do you look at?
- N terminus (usually around 9)
- C terminus (usually around 2)
- side chains with pKa values
