chapter 26 Flashcards
secondary alcohols are oxidized to? and under what conditions
ketones
refluxed under acidified conditions
the oxidizing agent in the oxidization of secondary alcohols
potassium dichromate
primary alcohols are oxidized to what, and under what conditions
oxidizing agent?
aldehydes
distilled under acidic conditions
potassium dichromate
can tertiary alcohols be oxidised
no
what group is present in the structure of both aldehydes and ketones
a carbonyl group
the position of the carbonyl group in a ketone and aldehyde
in a ketone, the carbonyl group is joined to two different carbons in the chain, while in aldehydes, the carbonyl group is found at the end of the carbon chain
the ending of a molecular structure of an aldehyde
CHO
aldehydes are oxidized to
carboxylic acids
conditions for the oxidization of aldehydes and the oxidizing agent
reflux under acidic conditions
potassium dichromate
when an aldehyde is oxidized, there is a color change in the dichromate solution from
orange to green
do ketones undergo oxidization
nope
why is the C=O bond polar
because of the difference in electronegativity values of O and C
nucleophile
a electron donor
aldehydes and ketones can be reduced to
the reducing agent for such reactions?
alcohols
sodium tetrahydridoborate (III) (NaBH4)
in nucleophilic addition, the C=O pie bond breaks in a ……………. manner forming a …………….. charged intermediate
heterolytic
negatively
in nucleophilic addition, the hydride ion is provided by
the NaBH4
Describe what happens in nucleophilic addition
lone pair on the hydride ion is attracted and donated to the partially positive carbon atom of the C=O bond. This forms a dative covalent bond
in nucleophilic addition, the C=O pie bond breaks in a heterolytic manner forming a negatively charged intermediate
the oxygen atom in C-O bond in the intermediate donates a lone pair of electrons to a hydrogen atom in a water molecule.
An alcohol is formed as a result
an aldehyde reacts with hydrogen cyanide to form
under what conditions
where do we get the hydrogen cyanide from
a hydroxynitrile
acidic conditions
NaCN
why is the reaction between an aldehyde and hydrogen cyanide important
it provides a way to extend the carbon chain length
on which atom is the lone pair in CN on
on C
brady’s reagent
a solution of 2,4-DNP dissolved in methanol and sulfuric acid
describe a test to identify a carbonyl group in either an aldehyde and a ketone
add a 5cm depth of a solution of 2,4-DNP to a clean test tube
add 3 drops of the unknown compound. leave to stand
a yellow/orange precipitate forms if there is a carbonyl group(aldehyde or ketone) present
if no crystals form when brady’s reagent is added to a solution containing a ketone or an aldehyde
add more sulfuric acid
how do we identify whether a carbonyl group is exactly in a certain molecule
the precipitate formed after adding Brady’s reagent is filtrated
then it is recrystallized
the melting point is then measured and compared with known values
tollen’s reagent
a solution of silver nitrate in aqueous ammonia
in the tollen’s reagent, what acts as the oxidizing reagent
Silver ions
an aldehyde is oxidized to
a carboxylic acid
if an aldehyde is present in the tollen’s reagent test, what happens
a silver mirror is formed
will the tollen’s reagent be able to identify ketones and why
no, because ketones cannot be oxidized further
if there are two carboxylic acids in a compound, the name changes to the corresponding alkane, with a………… added at the end
dioic acid
carboxylic acids can form hydrogen bonds with two compounds, what are these
water and other carboxylic acids
name the factor that decreases the solubility of carboxylic acids
an increase in the number of atoms in the non polar carbon chain
what happens to the solubility of carboxylic acids as the acid group(COOH) increases
the solubility increases further
carboxylic acids with up to 4 carbon atoms are all soluble in water, true or false
true
are carboxylic acids strong acids?
no they are rather weak acids
products formed when carboxylic acids react with metals
salt and hydrogen gas
products formed when carboxylic acids react with metals
salt and hydrogen gas
carboxylic acids react with metal carbonates to form
salt, water and carbon dioxide
carboxylic acid derivatives
compounds that can be hydrolysed to form the parent carboxylic acid
in hydrolysis, which bond breaks in a carboxylic acid derivative
the single bond between the carbon in the acyl group and a different group
suffix for acyl chlorides
oyl chlorides
how are acyl chlorides prepared
by reacting carboxylic acids with thionyl chloride
molecular formula of thionyl chloride
SOCl2
what are the products formed from the reaction of carboxylic acids with thionyl chloride
an acyl chloride, Sulphur dioxide and HCl gas
Both gases are toxic
acyl chlorides are very unreactive, true or false
false they are very reactive
acyl chlorides react by losing ….?
their chloride ion while retain the C=O bond
nucleophile
an electron pair donor
condensation reaction
a reaction in which two molecules react together to form a larger molecule with the elimination of a small molecule
acyl chlorides react with alcohols or phenols to form
an ester and HCl
acyl chlorides react with water to form
an carboxylic acid and HCl
why should the reaction between acyl chlorides and water be carried out under anhydrous conditions
because if not, the acyl chloride will react violently with water to form the carboxylic acid
acyl chlorides react with ammonia to form
Primary amide
acyl chlorides react with amines to form
a secondary amide
how are acid anhydrides formed
from the condensation reaction between two molecules of carboxylic acid
which is more reactive, an acyl chloride, or an acid anhydride
acyl chlorides
therefore acid anhydrides are more likely to be used in lab preparations while acyl chlorides might be too reactive
acid anhydrides react with alcohols to form
an ester and a carboxylic acid
functional group of esters
RCOOR
R stands for a carbon group
esters are named from backwards to forwards, true or false
true
esterification
the reaction of a carboxylic acid with an alcohol to form an ester and water
can carboxylic acids react with phenols to form esters
no they cannot, because they are not reactive enough to do so.
instead acyl chlorides and acid anhydrides are used
do esters react with acyl chlorides
no
acid hydrolysis of esters is the reverse of
esterification
in acid hydrolysis, the ester is heated under ……………… with ……………………..
reflux
dilute aqueous acid
in acid hydrolysis, the ester reacts slowly with water. but the reaction is sped up by ……………………
what acts as the catalyst
catalysis
the dilute aqueous acid
alkaline hydrolysis is also known as
saponification
in alkaline hydrolysis, the ester is heated under…………… with ……………… to form a ……………………. and an ……………….
reflux
aqueous hydroxide ions
carboxylate ion
alcohol
