McMurry (Kap. 15,2) Flashcards
How is the 3d structure of carboxylic acid?
It is similiar in some respects to ketones and alcohols - the carboxyl carbon is SP2 hybridized like the ketones.
The carboxylic group is therefore planar with the C-C=O and O=C-C bond angles at around 120 grader.
Why is the boiling point for carboxylic acid so high? (higher then alcohol?)
Because of its strong intermolecular forces (like hydrogen bonding) - most carboxylic acids exit as cyclic dimers held together by two hydrogen bonds.
acetic acid = BP (117,9 grader celcius)
ethanol = BP (78,3 grader celcius)
there is a significant diference between the BP of carboxylic acid and alcohol even though they both contain 2 C-atoms.
What are the acid/base properties of carboxylic acid?
As the name alludes to - it is an acid.
they react with bases (such as NaOH and NaHCO3) to yield metal carboxylate salts (see page 534 for illustration).
Metal carboxylate salts form when a carboxylic acid reacts with a metal or a metal compound, such as a metal hydroxide, metal oxide, or metal carbonate.
A list of the Ka-values for carboxylic acids is given in page 535.
How is the solubility of carboxylic acids?
With more then 6 C-atoms (only slightly soluble in water).
THOUGH the alkali metal salts of carboxylic acids are often highly soluble in water.
Where is carboxylic acid placed in the hieracia of acid strengths compared to other function groups?
like alcohols, phenols, mineral acids (for example HCl)
Mineral acids are much stronger then carboxylic acid.
Carboxylic acid is much stronger acids then alcohols and phenols.
Why is carboxylic acid much stronger acid then alcohols even if they both contain -OG groups?
An alcohol dissociates to give a negative charge on one O atom.
An carboxylic acid dissociate to give a negative charge delocalized over two O atoms - in resonance terms, a carboxylate ion is more stable, lower in energy and more favored in the dissociation equilibrium
(also a more stable acid is a stronger acid, because if the corresponding base is also more stable, then the more stable base is a weak base).
How does the resonance hybrid affect the bond lenghts in the carboxylic acid?
In the deprotonated/ionic form, the electrons are delocalized between the two O atoms.
(C-O) = 134 pm
(C=O) = 120 pm
But in the hybrid resonance structure both the bonds are (127 pm).
