Chapter 26 Carbonyls And Carboxykic Acids Flashcards
Carbonyl functional group?
But how do you still name the others
Carbonyl functional group is c=o, other things have this but yh still call them aldehyde functional group etc
What oxidation reactions can be undergone to create carobynyl group compounds
Primary oxidisation of alcohol to give aldehyde and then carbon
Secondary alcohol to form a ketone
Oxidation in regards to ketones and aldehydes? What and why not
An aldehyde can oxidise using acidified potassium dichromate etc to form carbon
But ketone can’t - THIS BECAUSE THERE US NO HYDROGEN ATTACHED TO THE OXYGEN BEARING CARBON, so can’t oxidise.
So one way to distinguish between aldehydes and ketones?
Oxidise them, the aldehyde becomes orange to green, and ketone stays orange!
What is special about carbonyl group compared to c=c on alkenes?
-C=o is POLAR due to electronegativity differences between them .
- however c=c is non polar
- as a result c=o can attract NUCLEOPHILES which are electron donors (to the slightly positive end)
Which results in NUCLEOPHILIC ADDITION ACROSS THE BOND
whereas the c=c is non polar so can only attract electrophoresis, which are electron pair acceptors (positives thst attracted to high electron dense areas)
This is electriplhilic addition
What reactions do aldehydes and ketones take part in to become what ? (Opposite)
REDUCTION to become alcohols again!
2 ways of reduction , what are reagents?
What are products
Reduction by NABH4 / H2O
Is basically 2[H]
- Forms alcohols
2) reduction by hydrogen cyanide
- made by NACN/H2SO4 in the first place
Forming a HYDROXYNITRILE
How to do reduction reactions bath nabh4 and hcn
1) NABH4 considered ti have hydride ion H-, which reacts with partially positive carbon to form dataive covalent
2) the carbon doubled bond one hetrolhticsllt breaks forming negative oxygen intermediate
3) this part important, the water molecule (making aqueous ) either H+ here or show full the bond between h and o heterolytifsllt splitting forming H+ and then the lone pair on oxygen donating
Should get some sort of alcohol!
2) somas thing except the HCN is actually made by NACN and h2so4, then the Lone pair on CN- is given to the c dative bond etc
Why is the reaction ti from a HYDROXYNITRILE important?
Important because it makes a way to increase the CARBIN CHAIN LENGTh, which we normally can’t do.
Make sure in CN- where is the -?
It’s actually on the CABRON! Not the n!
What does 2- 4 DNP STAND For and what test
Stand for 2-4 dinitrophenylhydrazine, or BRADYS reagent
Tests for presence of carbonyl group.
If found, then a yellow / orange PRECIPATE is formed for carbonyl= aldehyde or ketone group is there
In practice what else is used when using 24 dnp
Methanol and sulfruic acid
Why can 24 DNP hazardous (dk if need to know)
Friction or a sudden blow can cause it to blow
After identifying you have an aldehyde or ketone, how to distinguish then?
Tollens reagent Is a solution if SILVER NITRATE IN AQEOUS AMMONIA
In presence of aldehyde a silver mirror formed,l if ketone, nothing
What happens in a reaction with tollens reagent and aldehyde or ketone?
The tollens regent contains silver ions , which reduce to become silver solid, and the aldehyde will oxidise to form a carboxylic acid
Ketone can’t oxidise remember = no hydrogen! So no reaction
How to only use 2-4 DNP to determine what substance eyiubhave
It confirms alidade ketone, now filter this from the solutions to get your 24 di nitro hydrazone (this is after reacted with thr carbinyl ).
Now recrystallise to fork pure sample of crystals, and determine the melting point .
Compare this to known values to find what substance this hydrazone came frkm
Carboxulic acid functional group?
Still CARBOXYL not carbinyl and HYDROXy!
These both have dipoles too!
Solubility of carboxylic acids?
Dicarbicylic acids?
Because of the polar nature and electronegative atoms hydrogen bonds can be made
- thus carbixykic acids up to 4 carbons are SOLUBLE
- after this the effect of non polar chain is greater (effect of hydroxyl group is weaker compared, less soluble)
Ofc this changes when there are TWO CARBOYXL functional groups, solubility increases
Where hydrogen bond formed in carbkxylic scid and water?
This formed between the c=o and water
Or oh and and a water, can be both
Hydrogen bond from a lone pair to a partially positive hydrogen
Cabroxykic acids weak or string?
If so what equation fir dissociation
Classier as weak acids (but stringer than phenol I think) and shanc are the strongest
Thus it reversible reaction, partially dissociated to form H+ ions and a carboxylate ion
How to test for a carobykic acid
Carbixykic acids are stronger than phenol so reacts with weak base sodium carbonate ti give off effervescence
However phenol to weak so this don’t happen, only react with sodium hydroxide that’s it
= only carbixykic acids are string enough organic that react with carbonates in neutralisation
Reacts in all normal redox reactions, forming salt and carboxylate ending , what are these
Neutralisation
Metal
Metal carbonate
Metal oxide
Metal hydroxide
Etc
How to show reaction of carbixykic acid with something like metal
Show the ions joined together! Decofbe all observations
Remember what state are group 1 carbonates normally?
Aqueous
