Carboxylic acids. 1 C: formic acid, methanoic acid 2 C’s: acetic acid, ethanoic acid 3 C’s: propionic acid, propanoic acid 4 C’s: butyric acid, butanoic acid. Aspirin : Should you take a daily dose?. (Prostaglandins F 2 a ).
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Aspirin : Should you take a daily dose?
Prostaglandins are involved in the regulation of a variety of physiological
phenomena, including inflammation, blood clotting, and the induction of labor. Aspirin act by blocking the biosynthesis of prostaglandins in the cell.
Electron-withdrawing groups stabilize a conjugate base,
making a carboxylic acid more acidic.
Electron-donating groups destabilize a conjugate base,
making a carboxylic acid less acidic.
Alpha Hydroxy Acids in Cosmetics
Carboxylic acids’ Derivatives
(cell wall transamidase)
NH3 + H2O NH4+ + OH-
RNH2, ArNH2 Primary, 1o Amines
R2NH, Ar2NH Secondary, 2oAmines
R3N, Ar3N Tertiary, 3o Amines
NaNO2 inhibits the growth of Clostridium botulinum.
Quote of The Day
Think like a wise man
but express yourself like
an ordinary one.
is the study of the three-dimensional structure of molecules.
Isomers : Different compounds that have the same
Stereoisomers : Isomers that have the same bonding sequence
but differ in the orientation of their atoms in space.
Specific rotation, [a] = amount (degrees) that a substance rotates plane polarized light expressed in a standard form.
Carvone from caraway: [α]D = +62.5º
Carvone from spearmint: [α]D = –62.5º
Lactic acid from muscle tissue: [α]D = +2.5º
Lactic acid from sour milk: [α]D = –2.5º
How can one identify enantiomerism?
All objects may be classified with respect to chirality (from the Greek cheir = hand):
Chiral = Objects that are different from theirs mirror image;
i.e. golf clubs, scissors; enantiomers are chiral.
Achiral = Objects that are identical with theirs mirror image;
i.e. a pencil, a T-shirt.
Chiral molecule : (R)-lactic acid
Achiral molecule : water
Chiral molecules have chiral center (or stereo or stereogenic center):
an atom attached to 4 different atoms or groups.
Designating the Configuration of Stereogenic Centers
The CIP system of nomenclature.
(R. S. Cahn, C. K. Ingold and V. Prelog)
The assignment of the prefixes depends on the
application of two rules:
The Sequence Rule
The Viewing Rule
The Sequence Rule
substituents, they are treated as an equivalent set of single-
bonded atoms. i.e. C2H5– < CH2=CH– < HC≡C–
The Viewing Rule
Twist the lowest
priority to the
If you have troubles looking at the stereocenter, try Fischer Projections.
Only two kinds of motions are allowed for Fischer projection.
1) Rotation on page 180˚ is allowed for Fischer projection.
2) One group can be held steady while the other three rotate in either
a clockwise or a clockwise direction.
Assigning R, S configurations to Fischer projections.
of lowest (4th) priority at the top or bottom of the Fischer
projection if it is necessary.
1 to 2 to 3, and assign R (clockwise) or
Compounds Having Two or More Stereogenic Centers
(+)-Pseudoephedrine and (-)-Pseudoephedrine are diastereomers of (+)-Ephedrine.
melting points, boiling points, solubities in solvent, etc.
Enantiomers: non-superimposable (different) mirror images; most of chemical and physical properties are identical.
Diastereomers: are stereoisomers that are not mirror images (all stereoisomers except enantiomers) and have different chemical and physical properties.
Relationships Between Stereoisomers
Cahn-Ingold-Prelog R/S notation = Specifies absolute configuration of a chiral center;
there is no correspondence between R and + or S and –
an achiral molecule with 2 or more chiral centers and
an internal plane of symmetry; the molecule is achiral.
Number of stereoisomers = a molecule with n stereogenic centers (and for which a meso isomer isn’t possible) will have 2n stereoisomers.
Resolution of Racemic Mixtures
one specific enantiomer leaving the other alone.
diastereoisomers. Once separated the diasteriosomeric
forms are converted back to enantiomers in separate
E (German, entgegen for opposite) to designate the stereoisomers.
One learns one’s most valuable lessons through hardships.