reações dos grupos carbonilicos

7/21/2019 Reaes dos grupos carbonilicos

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REACTIONS OF THEREACTIONS OF THE

CARBONYL GROUP INCARBONYL GROUP IN

ALDEHYDES ANDALDEHYDES ANDKETONESKETONES

L.O.:The mechanism o n!c"eo#hi"ica$$i%ion &eac%ions o ca&'on("

com#o!n$s

Ho) ca&'on(" com#o!n$s &eac%

)hen o*i$ise$ o& &e$!ce$.


2/17

A test for an aldehyde using Fehlings solution.a) In a clean test tube mix together equal volumes ofFehling's solution A and Fehling's solution B. The

resultant Fehling's test reagent should be a clear darblue solution.b) Add ! dro"s of this test reagent to # cm$ of sodiumcarbonate solution in a test tube containing a fe% anti&

bum"ing granules and then add # cm$ of ethanal or"ro"anal) to this same test tube.c) (arm the test tube gently for a""roximately t%ominutes in a beaer half filled %ith hot %ater and then

gradually bring the beaer of %ater to boiling andmaintain this tem"erature for a fe% minutes.d) sing the test tube holder* carefully lift the test tubeout of the boiling %ater and allo% its contents to stand

for several minutes.


3/17

Tollens silver mirror test

+re"are a sam"le of Tollens reagent by adding !

dro"s of sodium hydroxide solution to , cm$ of silvernitrate solution in a test tube. To this test tube add -ustenough dilute ammonia solution to dissolve the bro%n"reci"itate com"letely.

sing a beaer of hot %ater ! o/ to 0 o/)* gently%arm a""roximately ! cm$ of this test reagent in a testtube.

Add # dro"s of the aldehyde to the %armed testreagent in the test tube. (ait a fe% minutes and note%hat ha""ens.


4/17

/arbonyl grou"s consists of a carbon&oxygen double bond

The bond is "olardue to the difference in

electronegativity


5/17

/A1B2345 /26+2378 & 3/592+:I5I/ A77ITI23/A1B2345 /26+2378 & 3/592+:I5I/ A77ITI23

6echanism 3ucleo"hilic addition

8te" # /3; acts as a nucleo"hile and attacs the slightly "ositive /2ne of the /


6/17





7/17





8/17


A3I6AT97 69/:A3I86


9/17


(atch out for the "ossibility of o"tical isomerism in hydroxynitriles

/3; attacs from above

/3; attacs from belo%


10/17

+an( &e$!cin, a,en%s )i"" &e$!ce

-e%ones an$ a"$eh($es %o a"coho"s.

NaBH/so$i!m %e%&ah($&o'o&a%e/III0

0 ,ene&a%es %he n!c"eo#hi"e H12 %heh($&i$e ion.3&i%e %he mechanism o %he &eac%ion

o a -e%one4a"$eh($e )i%h H1

.


11/17

3i"" NaBH &eac% )i%h an a"-ene5

NO6 H1is &e#e""e$ '( %he e"ec%&on $e

/:,< /:/:2 > ,?:@ /:,


12/17

/A1B2345 /26+2378 & 197/TI23/A1B2345 /26+2378 & 197/TI23

9xam"le (hat are the "roducts %hen /om"ound C is reducedD

3aB:E

:,/26+237 C


13/17

/A1B2345 /26+2378 & 197/TI23/A1B2345 /26+2378 & 197/TI23

9xam"le (hat are the "roducts %hen /om"ound C is reducedD

/


14/17

O*i$a%ion

Fehling test (Cu2+).

Silver mirror test (Ag+)


15/17

Is i% mo&e $i8c!"% %o o*i$ise a-e%one %han an a"$eh($e5 3h(


16/17

T:9 8I591 6I1121 T98T

Tollens1eagent contains ?Ag3:$),@>

(hen an aldehyde is %armed %ith Tollensreagent* metallic silver is formed.

Aldehyde is oxidised to carboxylic acidand Ag>reduced to metallic silver

1/:2 > ?o@ & 1/22: oxidation

?Ag3:$),@> > e& & Ag > ,3:$ reduction

cli"
http://www.youtube.com/watch?v=muo3oQYKaxYhttp://www.youtube.com/watch?v=muo3oQYKaxY


17/17

F9:5I3G8 825TI23F9:5I3G8 825TI23

It contains a co""erII) com"lex iongiving a blue solution. 2n %arming* it %illoxidise aldehydes. The co""erII) is

reduced to co""erI) and a red "reci"itateof co""erI) oxide* /u,2* is formed.

Hetones do not react %ith Tollens1eagent or Fehlings 8olution

video ,
http://www.youtube.com/watch?v=0PBjqW93rcohttp://www.youtube.com/watch?v=0PBjqW93rco

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