Preparation of Salicylaldehyde

a lab report


A. Introduction
Salicylaldehyde (SA) can be prepared using a Reimer-Tiemann reaction, ie:


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reaction

This reaction proceeds through formation of a :CCl2 carbene as shown in reference 1.

I followed the procedure found in Vogel’s 3rd ed, page 703 (ref 2). The expected yield is 12g. My crude flowsheet for this preparation is shown below:



SA preparation flowsheet

B. Apparatus
3-neck 1000 ml RBF (24/40)
overhead stirrer
west condenser (24/40)
west condenser (19/22)
60 ml p-e addition funnel
hotplate
thermocouple w/readout
2-quart waterbath (steel bowl)
distillation head (24/40)
distillation head (19/22)
vacuum adapter (19/22)
adapter (24/40 to 19/22)
100 ml RBF (19/22)
25 ml RBF (19/22)
cooling water (iced) supply
1000 ml heating mantle
100 ml heating mantle
aluminum foil
fiberglass insulation blanket
thermometer good to 200°C
steam distillation apparatus:
1. 500 ml separation funnel (steam trap)
2. 5mm x 30cm glass tube
3. 2-hole rubber stopper
4. ¼” latex rubber tubing, ~2’
5. hot plate
6. pressure cooker
7. thermometer adapter (19/22)
8. adapter (24/40 to 19/22)
9. 2ea glass plugs (24/40)

125 ml separatory funnel
250 ml separatory funnel
miscelaneous beakers

C. Reagents
28.4g phenol (aqueous, 88%)
40.5 ml chloroform
80g NaOH
water
1M H2SO4 (~500 ml)
dichloromethane (~ 85 ml)
anhydrous MgSO4
sodium bisulfite (or sodium metabisulfite)

D. Procedure

1. Reaction
The reaction apparatus was set up as shown below. The 2nd picture shows the utilities outside the hood that were required for support.


SA reaction setup



SA utilities – outside the hood

To the 1000ml RBF was added a warm solution of 80g NaOH dissolved in 80 ml of water. To that was added a solution of 28.4g of 88% phenol dissolved in 21.6 ml of water. The water bath was kept at about 65°C. 40.5 ml of chloroform was added to the 60ml p-e funnel attached to the outlet of the condenser using a notched rubber stopper.

40.5 ml of chloroform was added to the p-e funnel. With the overhead stirrer running at 222 rpm the chloroform was added slowly over a period of ½ hour. I attempted to keep the temperature of the reactants at 65-70°C per procedure by adding boiling water to the water bath. However, the temperature ranged from 59°C to 64°C. I didn’t turn on the hotplate as I was afraid of a possible runaway. This never happened and I never did have to cool the bath. The mix was then heated with the water bath boiling for another hour.

During the addition of the chloroform the reactant mix turned red and eventually turned to a dark brown, looking very much like beef gravy. Chloroform refluxed all the while. There was foaming for a time but it was not a problem due to the generous freeboard of the 1000ml RBF. At cleanout of the RBF a disc of tar about the size of a 50 cent piece was found at the bottom of the flask. It was soluble in alcohol and a tiny bit gave a strong yellow coloration - dare I say à la Perkin. Pictures of the reactants at various stages are shown below:


SA reactants – later – after all chloroform added


SA reaction – during final 1 hour hold

2. Workup
The workup for this synthesis is very long, nearly discouraging me from even starting this synthesis. Garage chemist described it succintly as “a pain.” See the flowsheet above.

a. Steam distillation to remove unused chloroform
This was performed in the 1000ml pot as shown below. I recovered no chloroform. I believe that any unused chloroform escaped from the 24/40 West condenser (on ice-water). Vogel calls for “an efficient (double wall) reflux condenser.” I don’t have one of those. The picture below shows the steam distillation.



Steam distillation to remove excess chloroform

b. Acidification
The pot mix was then acidified with ~250 ml of 1M H2SO4. The color of the mix lightens considerably during the acid addition.


c. Steam distillation to remove the SA/unreacted phenol

A second steam distillation was now done to remove the SA and any unreacted phenol as shown below:



2nd steam distillation to remove SA/phenol

d. Extraction
The distillate from the 2nd steam distillation was now extracted with 25ml x 25ml dichloromethane (DCM) to remove the SA/phenol from water. This is shown below. The yellow liquid in the beaker is the first extraction, the clear liquid in the bottom of the funnel is the second extraction.



SA/phenol extraction with DCM

e. Distillation
The combined extracts are distilled to remove DCM. 45ml of good quality DCM was obtained for recycle. This is done using a water bath as shown below:



Removal of DCM by distillation

This report is continued on the next post due to the excessive number of images.


[Edited on 30-3-2015 by Magpie]

[Edited on 30-3-2015 by Magpie]

[Edited on 31-3-2015 by Magpie]

Continuation

f. Sulfite adduct formation
The sulfite adduct is now formed to separate the salicylaldehyde from the excess phenol. This is done by adding 2X its volume of saturated aqueous sodium bisulfite (I used Na metabisulfirte). Since the mix is biphasic Vogel called for this to be shaken vigorously for 1/2hr, then allowed to sit for 1 hour. The resting product is shown below:


SA bisulfite adduct – post shaking

g. Separation of the adduct by filtration
The adduct, a pure white solid, was then separated from the water and phenol by filtration using a 7cm Buchner filter. It is shown in the picture below:


SA adduct filtered

At one point during the filtration I did not get the filter paper properly sucked down (sealed) against the ceramic base. Consequently I lost some product here – possibly as much as a gram. The dried adduct was weighed (17g), indicating the presence of 9.2g of SA.

h. Recovery of the salicylaldehyde
The SA is recovered by decomposition of the adduct. This is done by adding 1M H2SO4 then gently warming in a water bath. I added 75ml of the acid. During the warming I got too aggressive with the heating in an effort to fully decompose the adduct to SA and SO2, forgetting to follow the direction of “warming.” As a consequence I believe I lost 2-3g of product via steam distillation up the hood vent. I could visibly see that the volume of yellow oil on the bottom of the flask had decreased. Warming the adduct in the water bath is shown below:


SA bisulfite adduct decomposition

i. Extraction
The SA/water product was then extracted with 25ml x 15ml of DCM. The extract is shown drying overnight over anhydrous MgSO4 in the picture below:



SA in DCM being dryed

i. Distillation
The next day the DCM was removed by distillation. Following this with the pot heavily insulated with a fiberglass blanket shrouded in aluminum foil, the SA was distilled. The product was captured that boiled in the range of 193-196°C. Literature value (Vogel) is 195-197°C. Pictures of the distillation apparatus, the thermometer at product take-off, and the salicyaldehyde product are shown below:


SA distillation


SA distillation temperature


SA product

E. Results
My yield was a disappointing 6g. The yield would have been better if not for the losses described above. The expected yield (Vogel) is 12g. Even this is only a 37% yield.

F. Conclusions
1. Salicylaldehyde can be successfully made using the Riemer-Tiemann reaction and Vogel’s procedure. My poor yield can certainly be much improved.
2. DCM can be successfully substituted for diethyl ether as the extractant in this synthesis. Other than its obvious advantages I think DCM gives cleaner separations, and is quite recoverable by distillation.
3. My homemade overhead stirrer performed satisfactorily.

G. Discussion
My reasons for doing this synthesis are many: (1) I wanted to perform a complex synthesis involving relatively benign chemicals as I have been out of the lab for ~3 months due to a health issue which has since been satisfactorily resolved, (2) I had 500ml of reagent grade phenol that I’ve had for over 5 years without use, (3) I wanted to find out how well DCM could be substituted for diethyl ether for extraction, (4) I wanted to test out my new stepper motor overhead mixer, and (5) JimmyMajesty’s work with aldehydes piqued my interest in isolating an aldehyde by sulfite adduct. Also I wanted to perform a name reaction new to me. I found the Riemer-Tiemann mechanism to be fascinating; and carbenes are always fascinating.

Salicylaldehyde has a smell very similar to benzaldehyde, but with a little bite and is not as sweet or strong. One source said it smells of bitter almond.

H. References
1. http://en.wikipedia.org/wiki/Reimer%E2%80%93Tiemann_reaction
2. Practical Organic Chemistry, 3rd edition, by Arthur I. Vogel, 1956 (see forum library)

Questions, comments, and suggestions are welcomed.


[Edited on 30-3-2015 by Magpie]

[Edited on 30-3-2015 by Magpie]

[Edited on 31-3-2015 by Magpie]

That looks very interesting, Magpie, but I think I'll pass on trying it myself.

Thank you blogfast, morganbw and Loptr.

I hope JimmyMajesty tries isolating his acetaldehyde by sulfite adduct.

[Edited on 31-3-2015 by Magpie]

Very nice Magpie!

Is there any specific reason you liberated the aldehyde in acidic conditions, thereby forming SO2?
Or just because you can as you have one of the nicest fume hoods I've seen on here ?

I would also recommend the Mg formylation as an alternative it is a breeze.

Thank you waffles and lullu. I used the Reimer-Tiemann for the reasons stated in the "Discussion" section of my report. But thanks for the information on o-formylation.

lullu, that is an interesting question about using acid for liberation of the aldehyde from the adduct. I've seen for other syntheses, and expected, that this would be done with a base. I just followed the direction in Vogel in using the acid, 1M H2SO4.

Loptr, I can't say for sure for salicylaldehyde (yet) but for benzaldehyde it is surprisingly stable. I would expect SA to be similar. But for butyraldehyde and propionaldehyde my experience is that they oxidize easily.

Quote: Originally posted by Waffles SS

Are you sure Benzaldehyde is stable in oxidation?

Hey Magpie,

Well done!

I tried to isolate the acetaldehyde as the bisulhite adduct.
It needs time for the formation and for the decomp also, also you can precipitate the bisulphite without the adduct if there is an ethanol carry over and there is always some with the catalytic method. So I do not isolate the acetaldehyde rather use it as a gas, but if you need some more info on the acetaldehyde adduct I surely can do some experiments for you

Thanks, Captain.

I attempted this preparation, with the differences being using Kmetabisulfite , crashing more adduct with acetone and ofcourse a huge experience and knowledge gap between me and magpie (bless his soul).


The reaction mixture formed a thick slurry of goop, i think a flatbottom 3neck with a large stirbar would have been much preferable.

The steam distillation seemingly went quite well, i stopped after the drips reached clarity.

This is where it started to get wierd, the DCM extracted organics from the steam distillation were VERY red, but sufite reduced this to a dirty yellow.
After stirring the organics with metabisulfite solution for 4h, nothing had precipiated (but it had become homogenous), so i decided to evaporate it. and chill. After filtering i added 3x the filtrates volume of acetone to crash out more of the adduct while hopefully keeping the phenol dissolved. This made it very yellow but seemingly worked well.


Sadly i dont have an image of the acid degradation or distillation of the salicylaldehyde, but notably after extracting the acidic solution with DCM it again turned red. Distilling didnt separate this color.

Final yield was 15% assuming the distillate is mostly pure.
Dont do this preparation yourself, make/get formaldehyde and do the Mg mediated formylation, this sucked

Small thing of note: a solution of oxone was used to rid the recovered DCM of SO2, worked great.

[Edited on 19-1-2021 by RustyShackleford]

Quote: Originally posted by Pumukli

Maybe the red color means there is unreacted phenol that is oxidized. Phenol distills with steam as far as I know. On the other hand I read somewhere that hydroxy aldehydes resist oxidation pretty well. Salicylaldehyde was explicitely mentioned. Maybe it is only true at room temp, I 'm not sure.