Lecture 1 - Intro Flashcards
How can you improve a drug?
By utilizing knowledge of or determining structure activity relationships (SAR)
Medicinal chemists study _____
SAR, structure activity relationships
What is qualitative SAR?
The relationship between the structure and the pharmacological effect
What are sigma bonds?
Single bonds formed by overlap of hybrid orbitals
Do sigma bonds usually have complete freedom of rotation?
Yes
What do P orbitals form?
Pi bonds
Do pi bonds have complete freedom of rotation?
No
What is electronegativity?
The ability to attract electron density
What are the most important electronegative atoms in med chem?
- Halogens (F, Br, I, & Cl)
- Nitrogen
- Oxygen
What are the 2 ways that electron density can move through a molecule?
1) Resonance - movement of electron density through pi bonds (through a conjugated system)
2) Induction - movement of electron density through sigma bonds (through saturated carbons)
What determines if a functional group is ED or EW?
- If the donating or withdrawing happens through resonance or induction
- Also, the electronegativity, presence of lone pairs of electrons, multiple bonds, and the molecular geometry
Which functional groups are ED when resonance and EW when induction?
-OH, -OR, -NH2, and -NR2
Which functional groups are always EW, whether resonance or induction?
-COOH, -COOR, -COR, -CHO, -SOR, -SO2R, -SO2RNR2, -NO2, and -CN
Which functional groups are ED when induction?
-O-, -S-, -COO-, and -CH3
Which functional groups are EW when induction?
-NH3+, -NR3+, -F, -Cl, -Br, and -I
Will a molecule be EW or ED when it is attached to a carbon or sulfur that is double bonded to an oxygen?
Strongly EW
What are the rules for pH and pKa if you want to ionize free acid (HA) to conjugate base (A-)?
pH > pKa
What are the rules for pH and pKa if you want to minimize the ionization of HA to A-?
pH < pKa
What are the rules for pH and pKa if you want to ionize free base (B) to conjugate acid (HB+)?
pH < pKa
What are the rules for pH and pKa if you want to minimize the ionization of B to HB+?
pH > pKa
What happens to ionization when pH = pKa?
You get 50% ionization
It is always assumed that the solvent is _____
Water
How can you explain why the proton of COOH is acidic?
Its inductive effects in the neutral form and the resonance effects in the ionized form
Why are drugs usually marked in a salt form?
Because they are easier to make into solid dosage forms and they dissolve more readily in water
What is an example of a strong acid?
HCl
What are 2 examples of weak acids?
Maleic & succinic acid
What are 2 examples of strong bases?
NaOH and KOH
What is an example of a weak base?
NaH2PO4 (monosodium phosphate)
When you see “HCl” on a label does that mean there is acid in the drug formulation?
NO, it means HCl was mixed with the original drug to form a salt; there is no free HCl in the compound
What does hydroscopic mean?
Absorbs atmospheric water
What is a substituent?
An atom or group of atoms substituted in place of an H atom on the parent organic compound
What are you supposed to do when asked to make a substitution on the exam?
Replace a hydrogen atom on the parent molecule with a functional group
Alkanes have a ____ carbon center
Tetrahedral
Alkanes are ____ hybridized
sp3
Are alkanes polar? Hydrophobic or hydrophilic?
Nonpolar and hydrophobic
Are alkanes ED or EW?
Always ED
Alkenes are ____ hybridized
sp2
Are alkenes polar? Hydrophobic or hydrophilic?
Nonpolar and hydrophobic
What is the geometry of alkenes?
Planar
Are alkenes EW or ED?
Can be either depending on substituents
Alkynes are ____ hybridized
sp
Are alkynes polar? Hydrophobic or hydrophilic?
Nonpolar and hydrophobic
Are alkynes EW or ED?
Mostly EW
Alkanes and alkenes can only form _____ interactions
Van der Waals
Can alkanes and alkenes form bonds with water?
No, so they are not water soluble
What does a larger and more branched alkyl chain mean for hydrophilicity and lipophilicity?
Less hydrophilic and more lipophilic
Halogenated hydrocarbons are generally ___ hydrophilic than the alkyl form
Less
Which halogen is the most electronegative and which is the least?
- Most = F
- Least = I
Which halogen is the smallest and which is the largest?
- Smallest = F
- Largest = I
Are halogenated hydrocarbons hydrophobic or hydrophilic?
Hydrophobic
Are halogens of saturated hydrocarbons EW or ED by induction?
EW
When is OH ED?
Through resonance
When is OH EW?
Through induction
Are alcohols H-bond donors or acceptors?
Both
What happens to alcohol solubility when the length of a hydrocarbon increases?
Solubility decreases, but it depends on the position of the OH
Are phenols or aliphatic alcohols more acidic?
Phenols
Are alcohols acidic?
Not really
What is the typical pKa of phenols?
9-10, but depends on other substituents
Are aromatic hydrocarbons hydrophobic or hydrophilic when they are unsubstituted?
Hydrophobic
Is a sulfhydryl group (-SH) polar?
Yes, but only weakly polar
Is SH ED or EW?
Always ED
Is R-SH or R-OH more acidic?
R-SH because it is more willing to give up it’s proton
Are ethers polar?
Yes, weakly
Are thioethers polar?
Yes, weakly
Is alkoxy (-OR) EW or ED?
Both
Is thioalkoxy (-SR) EW or ED?
ED
Is sulfoxide ED or EW?
Always EW because it is a sulfur w/ a double bonded oxygen
Does sulfoxide have a lone pair of electrons?
Yes
Is sulfoxide polar?
Yes, highly
Is sulfone ED or EW?
Always strongly EW
Is sulfone polar?
Highly polar
Acetone is ___ hybridized
sp2
Is a carbonyl (C=O) polar?
Yes
Are aldehydes and ketones EW or ED?
Always EW
What are aldehydes and ketones in rapid equilibrium with and what does this form?
- In equilibrium with alcohol
- Forms hemiacetal and hemiketal
Are amines polar?
Yes
What types of interactions can amines form?
- H-bonds
- Dipole-dipole
- Ion-dipole
Is the neutral form of amine EW or ED?
- ED through resonance
- EW through induction
Is the nitrogen of amine acidic or basic?
Basic, so it can accept a proton
What types of interactions can carboxylic acids form?
- H-bonds
- Dipole-dipole
- Ion-dipole
Are carboxylic acids polar?
Yes
Are carboxylic acids EW or ED?
- EW when in neutral form
- ED when in anion form
Should a carboxylic acid be used when doing a substitution in a molecule that is EW?
No, because at physiological pH it readily deprotonates, making it ED
Are esters polar?
Yes
What types of interactions can esters form?
Only H-bonds with water
Are esters EW or ED?
Always EW
What is important to note about RCOOR’ (ester)?
- Susceptible to hydrolysis
- Catalyzed by esterases
- Frequently used a prodrug to facilitate the absorption of carboxylic acid drugs
Are amides polar?
Yes
What types of interactions can amides form?
- H-bonds with water
- Dipole-dipole
Are amides EW or ED?
Always EW
Is the N of RCONR2 (amide) basic?
No because the lone pair of electrons forms a resonance structure and is not available to accept a proton
Are amides acidic or basic at physiological pH?
Neutral
Nitriles and carbonates have properties similar to _____
Esters
Carbamates have properties between ____ and _____
Esters and amides
Ureas have properties similar to _____ and are ___ stable
- Amides
- Very
Are aminidines and guanidines polar?
Highly polar
What types of interactions can aminidines and guanidines form?
- H-bonds
- Dipole-dipole
- Ion-dipole with water
Are aminidines and guanidines EW or ED in the neutral form?
- Aminidines are EW
- Guanidines are weakly ED and weakly EW due to the electronegativity of nitrogen
Are aminidines and guanidines EW or ED in the ionized form?
- Aminidines are EW whether negative or positive
- Guanidines are EW whether negative or positive
Are aminidines and guanidines more or less basic than amines?
More
What should you use if you want to add something to a molecule that is EW?
Nitro
Is a nitro polar?
Only slightly
Are nitros EW or ED?
Highly EW
Can the negative O on a nitro accept an H+?
No
Sulfonic acids have properties similar to ______
Carboxylic acids
Are sulfonic acids EW or ED?
EW
Are sulfonic acids or carboxylic acids more polar?
Sulfonic acids
Sulfonamides have properties similar to _____
Amides
Are sulfonamides EW or ED?
EW
Are sulfonamides or amides more acidic?
Sulfonamides
Which molecules are commonly involved in heterocycles?
N, O, or S
What are the requirements for a compound to be aromatic?
- Cyclic
- Planar
- Delocalized conjugated
- # of electrons in p orbitals capable of forming pi bonds satistfies 4n + 2
What is needed for a compound to be considered delocalized conjugated?
- Every atom in ring has p orbital that can form pi bonds
- Every atom is sp2 hybridized
Are the interactions between aromatic rings considered dipole-dipoles interactions?
No, because an aromatic ring has more than 2 poles
What are the 3 types of aromatic/pi stacking interactions?
- T-shaped or edge to face
- Parallel displaced
- Sandwich