THEORY ESTERIFICATION REACTIONS OF VANILI PDF

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EXPERIMENT 3: ESTERIFICATION REACTIONS OF VANILIN ORGANIC CHEMISTRY II (CHM 557) UNIVERSITI TEKNOLOGI MARA (UITM) Objective 1) To identify each compound for acidic and basic conditions. 2) To determine percentage yield of the product and melting point of the product. 3) To identify the functional group and structure of product. Introduction Vanillin is a phenolic aldehyde, an organic compound with the molecular formula C8H8O3. Vanillin is an organic crystal that forms outside the vanillin bean and the extraction of naturally occurring vanillin is not only expensive but highly inefficient. Therefor vanillin can be produce by synthetically of vanillin with same identical structure in large among. The functional group in this molecule is ether, aldehyde and phenol.

Carboxylic acids react with alcohols to form esters through a condensation reaction which is known as esterification. Fischer esterification proceed very slowly in absence of strong acids, but they still reach the equilibrium when an acid and an alcohol are refluxed with a small amount of concentrated sulphuric acid and sodium hydroxide. Ester synthesis also can be accomplished by the reaction of an alcohol with an anhydride. By using anhydride we do not used strong acid because strong acid may cause side effect reaction. Esters undergo saponification which refluxing an ester with aqueous sodium hydroxide which produces an acetate. In this experiment infrared spectroscopy was used to determine the functional group of product. One of the most common application of infrared spectroscopy is to the identification of organic compounds that able to form bonding. Vibrating bonds absorb infrared energy at a frequency that corresponds to the vibrational frequency of the bond. If the frequency of the radiation matches the vibrational frequency, the bond will absorb the

radiation. The amplitude of the vibration will increase. The bonds in molecules are vibrating, and the vibrational energy is quantized. The bonds can stretch and bend only at certain allowed frequencies. Each functional group has vibrational frequencies in a small region of the IR spectrum, so IR spectra give us information about the functional groups that are present To identify the structure of product in this experiment, we were used Nuclear Magnetic Resonance spectroscopy. The theory of the NMR was involve of nuclei of some isotopes of many elements in which H that absorb electromagnetic radiation in the radiofrequency (Rf) region of the spectrum when they are placed in a strong magnetic field. The number of signals in an NMR spectrum corresponds to the number of distinct types of hydrogen atoms in a molecule. The NMR signal of a hydrogen nucleus is not split by other hydrogen atoms that are the same as itself Reaction Mechanisms: Base-Catalysed Mechanism

Figure 1. Mechanism for the base-catalyzed esterification of vanillin Ac i dCa t a l y s e dMe c hani s m

Fi gur e2.Me c ha n i s mf o rt hea c i dc a t a l y z e de s t e r i fic a t i onofv a ni l l i n

Method A. Preparation of 4-Acetoxy-3-Methoxybenzaldehyde (Vanillyl Acetate) 1) 1.50g of vanillin was dissolved in 25mL of 10% sodium hydroxide in 250mL Erlenmeyer flask. 2) 30 g of crushed ice and 4.0mL of acetic anhydride was added. 3) The stopper was placed and shake the flask for 20 minutes. 4) The precipitate was filtered by using bunchier funnel and the solid was washed using 5mL portion of iced cold water. 5) The solid was recrystallized from 95% ethyl alcohol. The mixture was heated in hot water bath about 60°C to avoid melting the solid. 6) After the crystal dry, it was weigh and the melting point (77-79°C literature point) was obtained. 7) The IR and NMR was determined. B. Esterification of vanillin in presence of acid. 1) 1.50 g of vanillin was dissolved in 10mL of acetic anhydride in 250 mL Erlenmeyer flask. 2) The mixture was stirred until the mixture was dissolved. 3) While stirring the mixture, 10 drops of 1.0M sulphuric acid to the reaction mixture. 4) Stopper the flask and shake the mixture for one hour 5) The flask was cooled in iced water bath for 4-5 minutes. 6) 35 mL of iced cold water was added to the mixture in the flask. 7) Tightly stopper the flask with a clean rubber stopper and shake vigorously for 10-15 minutes. 8) The product was filtered by using Buchner funnel and the solid was washed with 5mL potions of ice-cold water. 9) The crude product was recrystallized from hot 95% ethanol. The crystal was allowed to dry. 8) The mass and melting point of crystal was obtained. 9) NMR and IR was determined.

Re s ul t s : Ta bl e1 .Yi e l da ndme l t i n gp o i nto fp r od uc t s . Mas spr oduc t( g)

Mol e s

% Yi e l d

MPexp

MPtheo

Ba s e Ca t al y z e d

2 . 84 53g

0 . 00 1 2mol e s

%

8 6-8 7° C

77 7 9° C

Ac i dCa t a l yz e d

1 . 92 0 1g

0 . 0 00 8mo l e s

%

8 4-8 6° C

90 9 1° C

Discussion In this experiment, the main objective were able to achieve by identifying each compound for acidic and basic conditions. In acidic condition, the reaction may produce t r i e s t e rba s eont h et h e or e t i c a l .Wh i l ei nba s i cc o nd i t i on ,t her e a c t i onwi l lpr o du c e 4 Ac e t o x y 3 Me t ho xy b e nz a l de h yd e( Va n i l l y lAc e t a t e ) .Th ef u nc t i on a lgr ou pa nds t r u c t u r eof t hep r o du c ewa sa n a l y s i sb yu s i n gI Rs p e c t r os c op ya ndNMRs pe c t r o s c op y .Th es t r u c t u r eof t hepr o du c ewe r es h o wi nb e l o w.

The mass of the product obtained for acidic condition was 1.9200 g from mass theoretical product able to product 2.9613 g in which only 64.83%. The percentage yield was lower than the theoretical mass due to the loss the product during transfer between procedures and also may cause by incomplete in the reaction. While the mass of the product obtained for basic condition was 2.8453 g from mass theoretical product able to product 1.9461 g in which only 146.20%. The percentage yield was higher than the theoretical mass might be the product was not completely dry and contain some water molecule in the crystal product. It also may cause by the reaction occur produce other type product. There were di ffe r e n c e sb e t we e nt heme l t i n gp oi nt soft hea c i da ndba s e c a t a l yz e d r e a c t i on s .Th er a n g eofme l t i n gpo i nt sf o ra c i di cc on d i t i onp r o du c twa s86–87Chi g he rt h a n t het he o r e t i c a lr a n g e si nwhi c h7 7–7 8C.whi l et h er a n g eo fme l t i n gp o i nt sf o rba s i cc on d i t i on p r o du c twa s84–8 6Cl o we rt ha nt h et h e or e t i c a lr a n g e si nwh i c h90–9 1C.Thev a r i a t i o no f r a n g e si nd i c a t e si mp ur i t i e spr e s e n ti nt hep r o du c t .Th eme l t i n gp oi ntoft h ep r o du c tma yc a u s e b yt hemo l e c ul a rwe i g hta n ds t r uc t ur ebo nd i n gpr e s e n ti nt hep r o du c t .Ba s eo nt het he or e t i c a l s h o wt ha tmo l e c ul a rwe i g htf o ra c i d i cc on d i t i onpr od uc twa s2 96g / mo lhi g he rt h a nba s i c c o nd i t i onr e a c t i o npr od uc ti nwh i c h1 94 . 18g/ mo l .Th ehi g he rt h emo l e c u l a rwe i g htoft h e c o mpo un d, t hehi gh e rt h eme l t i n gpo i n toft hec omp ou nd . I ta l s oma yc a u s eb yt hei mpu r i t yo f t hepr o du c tf r omt her e a c t i on .Ev e n ,r e c r y s t a l l i z eha sbe e nd on e .

TheI Rs p e c t r ai nr e s ul ts h o wt h ea b s or p t i on so ft h ea c i da n db a s e c a t a l yz e dr e a c t i on s , r e s p e c t i v e l y .Bot hc on t a i nas t r o n gpe a kne a r1 75 0c m-1 t ha tc or r e s p on dst oaC=O s t r e t c h.I twa s i n di c a t e dC=O b on dsp r e s e nc ei nt hec o mp o und .I twa sr e pr e s e n tt he r ewe r ee s t e rfic t i o na lgr ou pi n t hep r od uc t .Bo t ha l s os h o wt h ea r oma t i cC=C s t r e t c h i n goft he16 00 c m-1 r a n g e .Thedi ffe r e nc e p r o du c tbe t we e na c i d i cc on d i t i ona ndba s i cc on d i t i onr e a c t i o nwe r epr o du c ti nba s i cc o nd i t i onpr o du c e a l d e h yd ei nwhi c hpr o du c et h epe a ki nr a n g e1 71 0t o1 68 5c m1. Fo rs omer e a s on ,wec a nob t a i npe a k f orCHf ora l ky lgr ou p. I tma yc a u s eb yr e a c t i o ni nc ompl e t e . Ba s eont her e s u l tf o rNMR s pe c t r o s c op ys h o wt h eHNMR s p e c t r af ort h eb a s ea nda c i dc a t a l yz e dr e a c t i on s ,r e s p e c t i v e l y .Nor ma l l yf ora l k a negr ou p–CH3wi l lp r o du c er e s u l ta r ou nd1PPM, s obo t ho ft h epr o du c tc on t a i na l k a neg r o up .Bo t hoft h epr o du c ts ho wap e a ka tr a n g ef r o m3 -4PPM t ha tc or r e s po n dst ot hee t h e rgr ou pa ndbe t we e n7–9pp mi n di c a t ea sa r o ma t i ch y dr o g e n ( s ) .Th e r e s ul to fNMR s p e c t r os c o p yf o rb a s i cc on di t i ons h o wsap e a ka t10PPM t h a tc or r e s po n dst oa n a l d e h yd egr ou p .Th epe a ka t10PPM i sp r e s e n ton l yi nt heba s e c a t a l yz e dpr o du c t .

Conclusion Throughout of the experiment, the product was obtain able to identify. The esterification reaction in acid or base produces different products. It appears that the acid-catalyzed product produces

a

triester

that

the

base-catalyzed

reaction

produce

4-Acetoxy-3-

Methoxybenzaldehyde. The yield for the reactions were 59% and 77% for the base and acidcatalyzed reactions, respectively. The yield percentage weight may be somewhat inflated due to impurities detected in the measurements. Reference 1. Esterification, Science Encyclopaedia of Science & Philosophy: Ephemeris to Evolution retrieve from https://science.jrank.org/pages/2573/Esterification.html. 2. Infrared Spectroscopy, retrieve from https://socratic.org/organic-chemistry-1/infraredspectroscopy/infrared-spectroscopy 3. Infrared Spectra of Some Common Functional Groups, (2018), Libretexts, retrieve fromhttps://chem.libretexts.org/Bookshelves/Organic_Chemistry/Map %3A_Organic_Chemistry_(McMurry)/Chapter_12%3A_Structure_Determination %3A_Mass_Spectrometry_and_Infrared_Spectroscopy/12.08_Infrared_Spectra_of_S ome_Common_Functional_Groups 4. Pavia, D.L.; Lampman, G.M.; Kriz, G.S.; Engel, R.G. Introduduction to Organic Laboratory Techniques: A

Small Scale Approach, 3rd ed.; Brooks/Cole Thomson

Learning: Belmont, 2012; pp. 507-509. 5. Mcmurry George et al, chapter 3.1, 3.2, spectroscopy & structure determination retrieve from https://sydney.edu.au/science/chemistry/~george/spectroscopy.html 6. https://www.sigmaaldrich.com/technical-documents/articles/biology/ir-spectrumtable.html

Question 1. Under different reaction media, vanillin undergoes esterification with acetyl chloride yielding two different products.

a) Based on the IR spectrum of vanillin, at what range should you observe the absorption signal of the hydroxyl group? b) Based on its 1H NMR spectrum, what is the expected chemical shift value for the methoxy group (OCH3)? What is its multiplicity? c) Draw the structures of the major products for the esterification of vanillin with acetyl chloride in: i. 10% NaOH solution ii. 1.0 M H2SO4 solution 2. Write the mechanism for the reaction between vanillin and acetyl chloride in 10% NaOH solution....