View source for Vanillin

{{chembox
| Watchedfields = changed
| verifiedrevid = 307517931
|   Name = Vanillin
|   ImageFile = Vanillin2.svg
|   ImageSize = 150px
|   ImageName = Vanillin
|   ImageFile1 = Vanillin-3d.png
|   ImageSize1 = 130px
|   IUPACName = 4-Hydroxy-3-methoxybenzaldehyde
|   OtherNames = Vanilin<br />Vanillic aldehyde<br />Methyl vanillin
| Section1 = {{Chembox Identifiers
|   SMILES = O=CC1=CC(OC)=C(O)C=C1
|   CASNo_Ref = {{cascite}}
| CASNo = 121-33-5
|   RTECS = YW5775000}}
| Section2 = {{Chembox Properties
|   Formula = C<sub>8</sub>H<sub>8</sub>O<sub>3</sub>
|   MolarMass = 152.15 g/mol
|   Appearance = White or lightly yellow solid<br />(usually in needles)
|   Density = 1.056 g/cm³, solid
|   Solubility = 1 g/100 ml (25°C)
| SolubleOther = THF 3.6 M, ethanol 2.3 M, methanol 4.16 M <ref>[http://oru.edu/cccda/sl/solubility/allsolvents.php?solute=vanillin Solubility of vanillin in non-aqueous solvents.]</ref>
| Solvent = [[THF]], [[ethanol]], [[methanol]]
|   MeltingPt = 80–81&nbsp;°C (353–354 K)
|   BoilingPt = 285&nbsp;°C (558 K)
|   Viscosity = ? [[Poise|cP]] at ?°C
  }}
| Section7 = {{Chembox Hazards
|   ExternalMSDS = [http://www.jtbaker.com/msds/englishhtml/v2775.htm External MSDS]
|   MainHazards = May cause irritation to skin,<br />eyes, and respiratory tract
|   NFPA-H = 1
|   NFPA-F = 1
|   NFPA-R =
|   FlashPt = 147°C
|   RPhrases = {{R22}}, {{R36}}.
|   SPhrases = {{S24/25}}.
  }}
| Section8 = {{Chembox Related
|   OtherCpds = [[Eugenol]], [[Anisaldehyde]], [[Phenol]]
  }}
}}
'''Vanillin''' is an [[organic compound]] with the molecular formula C<sub>8</sub>H<sub>8</sub>O<sub>3</sub>.  Its [[functional groups]] include [[aldehyde]], [[ether]], and [[phenol]].  It is the primary component of the extract of the [[vanilla]] bean.  It is also found in roasted coffee<ref>{{cite doi|10.1002/ffj.2730100102}}</ref> and the [[Chinese Red Pine|Chinese red pine]].  Synthetic vanillin, instead of natural vanilla extract, is sometimes used as a [[flavoring agent]] in foods, beverages, and pharmaceuticals.

Methyl vanillin is used by the food industry as well as [[ethylvanillin]]. The ethyl is more expensive but has a stronger note.  It differs from vanillin by having an ethoxy group (–O–CH<sub>2</sub>CH<sub>3</sub>) instead of a methoxy group (–O–CH<sub>3</sub>).

Natural "vanilla extract" is a mixture of several hundred different compounds in addition to vanillin.  Artificial vanilla flavoring is a solution of pure vanillin, usually of synthetic origin. Because of the scarcity and expense of natural vanilla extract, there has long been interest in the synthetic preparation of its predominant component.  The first commercial synthesis of vanillin began with the more readily available natural compound [[eugenol]].  Today, artificial vanillin is made from either [[guaiacol]] or from [[lignin]], a constituent of [[wood]] which is a byproduct of the [[paper industry]].

Lignin-based artificial vanilla flavoring is alleged to have a richer flavor profile than oil-based flavoring; the difference is due to the presence of [[acetovanillone]] in the lignin-derived product, an impurity not found in vanillin synthesized from guaiacol.<ref>According to [[#esposito1997|Esposito 1997]], blind taste-testing panels cannot distinguish between the flavors of synthetic vanillin from lignin and from guaicol, but can distinguish the odors of these two types of synthetic vanilla extracts.  Guaiacol vanillin, adulterated with acetovanillone, has an odor indistinguishable from lignin vanillin.</ref>

== History ==
Vanilla was cultivated as a flavoring by pre-Columbian Mesoamerican peoples; at the time of their conquest by [[Hernán Cortés]], the [[Aztecs]] used it as a flavoring for [[chocolate]].  Europeans became aware of both chocolate and vanilla around the year 1520.<ref name="#esposito1997|Esposito 1997">[[#esposito1997|Esposito 1997]]</ref>

Vanillin was first isolated as a relatively pure substance in 1858 by [[Nicolas-Theodore Gobley]], who obtained it by evaporating a vanilla extract to dryness, and [[recrystallization (chemistry)|recrystallizing]] the resulting solids from hot water.<ref>[[#gobley1858|Gobley 1858]]</ref> In 1874, the German scientists [[Ferdinand Tiemann]] and [[Wilhelm Haarmann]] deduced its chemical structure, at the same time finding a synthesis for vanillin from [[coniferin]], a [[glycoside]] of [[isoeugenol]] found in [[pine]] bark.<ref>[[#tiemann1874|Tiemann 1874]]</ref> Tiemann and Haarmann founded a company, Haarmann & Reimer (now part of [[Symrise]]) and started the first industrial production of Vanillin using their process in [[Holzminden]] (Germany). In 1876, [[Karl Reimer]] synthesized vanillin ('''2''') from [[guaiacol]] ('''1''').<ref>[[#reimer1876|Reimer 1876]]</ref>
{{center|[[File:Synthesis vanillin 3.svg|300px|]]<br />Synthesis of Vanillin by Reimer}}
By the late 19th century, semisynthetic vanillin derived from the [[eugenol]] found in [[clove]] oil was commercially available.<ref>According to [[#hocking1997|Hocking 1997]], synthetic vanillin was sold commercially in 1874, the same year Tiemann and Haarmann's original synthesis was published.  Haarmann & Reimer, one of the corporate ancestors of the modern flavor and aroma manufacturer [[Symrise]], was in fact established in 1874.  However, [[#esposito1997|Esposito 1997]] claims that synthetic vanillin first became available in 1894 when Rhône-Poulenc (since 1998, [[Rhodia (company)|Rhodia]]) entered the vanillin business.  If the former claim is correct, the authors of the latter article, being employees of Rhône-Poulenc, may have been unaware of any previous vanillin manufacture.</ref>

Synthetic vanillin became significantly more available in the 1930s, when production from [[clove oil]] was supplanted by production from the [[lignin]]-containing waste produced by the [[Sulfite pulping process]] for preparing wood pulp for the [[paper]] industry.  By 1981, a single pulp and paper mill in Ontario supplied 60% of the world market for synthetic vanillin.<ref name="#hocking1997|Hocking 1997">[[#hocking1997|Hocking 1997]]</ref>  However, subsequent developments in the wood pulp industry have made its lignin wastes less attractive as a raw material for vanillin synthesis.  While some vanillin is still made from lignin wastes, most synthetic vanillin is today synthesized in a two-step process from the petrochemical precursors [[guaiacol]] and [[glyoxylic acid]].<ref name="#esposito1997|Esposito 1997"/>

Beginning in 2000, [[Rhodia (company)|Rhodia]] began marketing biosynthetic vanillin prepared by the action of microorganisms on [[ferulic acid]] extracted from [[rice bran]].  At $700/kg, this product, sold under the trademarked name Rhovanil Natural, is not cost-competitive with petrochemical vanillin, which sells for around $15/kg.<ref>[[#rouhi2003|Rouhi 2003]]</ref> However, unlike vanillin synthesized from lignin or guaiacol, it can be labeled as a natural flavoring.

== Occurrence ==
[[File:Vanilla fragrans 2.jpg|thumb|left|These green seed pods contain vanillin only in its glycoside form, and lack the characteristic odor of vanilla.]]
Vanillin is most prominent as the principal flavor and aroma compound in vanilla.  Cured vanilla pods contain approximately 2% by dry weight vanillin; on cured pods of high quality, relatively pure vanillin may be visible as a white dust or "frost" on the exterior of the pod.

At lower concentrations, vanillin contributes to the flavor and aroma profiles of foodstuffs as diverse as [[olive oil]],<ref>[[#brenes1999|Brenes 1999]]</ref> [[butter]],<ref>[[#adahchour1999|Adahchour 1999]]</ref> [[raspberry]]<ref>[[#roberts1996|Roberts 1996]]</ref> and [[lychee]]<ref>[[#ong1998|Ong 1998]]</ref> fruits.  Aging in [[oak (wine)]] barrels imparts vanillin to some [[wine]]s and [[distilled beverage|spirit]]s.<ref>[[#viriot1993|Viriot 1993]]</ref>  In other foods, heat treatment evolves vanillin from other chemicals.  In this way, vanillin contributes to the flavor and aroma of [[coffee]],<ref>[[#blank1992|Blank 1992]]</ref> [[maple syrup]],<ref>[[#kermasha1995|Kermasha 1995]]</ref> and [[whole grain]] products including corn [[tortilla]]s<ref>[[#buttery1995|Buttery 1995]]</ref> and [[oatmeal]].<ref>[[#guth1993|Guth 1993]]</ref>

== Production ==
=== Natural production ===
Natural vanillin is extracted from the seed pods of ''[[Vanilla]] planifola'', a [[vine|vining]] [[orchid]] native to Mexico, but now grown in tropical areas around the globe.  [[Madagascar]] is presently the largest producer of natural vanillin.

As harvested, the green seed pods contain vanillin in the form of its β-D-[[glycoside]]; the green pods do not have the flavor or odor of vanilla.<ref>[[#walton2003|Walton 2003]]</ref>  
{{center|[[File:Glucovanillin.svg|270px]]<br />β-D-glycoside of vanillin}}

After being harvested, their flavor is developed by a months-long curing process, the details of which vary among vanilla-producing regions, but in broad terms it proceeds as follows:

First, the seed pods are [[blanching (cooking)|blanched]] in hot water, to arrest the processes of the living plant tissues.  Then, for 1&ndash;2 weeks, the pods are alternately sunned and sweated: during the day, they are laid out in the sun, and each night, wrapped in cloth and packed in airtight boxes to sweat.  During this process, the pods become a dark brown, and [[enzyme]]s in the pod release vanillin as the free molecule.  Finally, the pods are dried and further aged for several months, during which time their flavors further develop.  Several methods have been described for curing vanilla in days rather than months, although they have not been widely developed in the natural vanilla industry,<ref>[[#dignum2001|Dignum 2001]] reviews several such proposed innovations in vanilla processing, including processes in which the seed pods are chopped, frozen, warmed by a heat source other than the sun, or crushed and treated by various enzymes.  Whether or not these procedures produce a product whose taste is comparable to traditionally prepared natural vanilla, many of them are incompatible with the customs of the natural vanilla market, in which the vanilla beans are sold whole, and graded by, among other factors, their length.</ref> with its focus on producing a premium product by established methods, rather than on innovations that might alter the product's flavor profile.

Vanillin accounts for about 2% of the dry weight of cured vanilla beans, and is the chief among about 200 other flavor compounds found in vanilla.

=== Chemical synthesis ===
The demand for vanilla flavoring has long exceeded the supply of vanilla beans. {{As of|2001}}, the annual demand for vanillin was 12,000 tons, but only 1800 tons of natural vanillin were produced.<ref>[[#dignum2001|Dignum 2001]]</ref> The remainder was produced by [[chemical synthesis]]. Vanillin was first synthesized from [[eugenol]] (found in oil of [[clove]]) in 1874–75, less than 20 years after it was first identified and isolated. Vanillin was commercially produced from eugenol until the 1920s.<ref>[[#hocking1997|Hocking 1997]].  This chemical process can be conveniently carried out on the laboratory scale using the procedure described by [[#lampman1977|Lampman 1977]].</ref> Later it was synthesized from [[lignin]]-containing "brown liquor", a byproduct of the [[sulfite process]] for making [[wood pulp]].<ref name="#hocking1997|Hocking 1997"/> Counter-intuitively, even though it uses waste materials, the lignin process is no longer popular because of environmental concerns, and today most vanillin is produced from the [[petrochemical]] raw material [[guaiacol]].<ref name="#hocking1997|Hocking 1997"/> Several routes exist for synthesizing vanillin from guaiacol.<ref>[[#vanness1983|Van Ness 1983]]</ref>

At present, the most significant of these is the two-step process practiced by [[Rhodia (company)|Rhodia]] since the 1970s, in which guaiacol ('''1''') reacts with [[glyoxylic acid]] by [[electrophilic aromatic substitution]].  The resulting [[vanillylmandelic acid]] ('''2''') is then converted via 4-Hydroxy-3-methoxyphenylglyoxylic acid ('''3''') to vanillin ('''4''') by oxidative decarboxylation.<ref name="#esposito1997|Esposito 1997"/>
:[[File:Synthesis vanillin 4.svg|600px]]

In October 2007 Mayu Yamamoto of the International Medical Center of Japan won an [[Ig Nobel Prize]] for developing a way to extract vanillin from cow dung.<ref>[http://www.japanprobe.com/?p=2875 Japan’s 12th Ig Noble Prize Winner: Mayu Yamamoto & Dung Vanilla : Japan Probe<!-- Bot generated title -->]</ref>

== Uses ==
[[File:Vanilla extract.JPG|thumb|right|Vanilla extract]]
The largest use of vanillin is as a flavoring, usually in [[sweetness|sweet]] foods.  The [[ice cream]] and [[chocolate]] industries together comprise 75% of the market for vanillin as a flavoring, with smaller amounts being used in [[confection]]s and [[baked goods]].<ref>[[#fridge2004|FRIDGE 2004]], p. 33</ref>

Vanillin is also used in the fragrance industry, in [[perfume]]s, and to mask unpleasant odors or tastes in medicines, livestock [[fodder]], and cleaning products.<ref name="#esposito1997|Esposito 1997"/>

Vanillin has been used as a chemical intermediate in the production of [[pharmaceuticals]] and other [[fine chemicals]].  In 1970, more than half the world's vanillin production was used in the synthesis of other chemicals,<ref name="#hocking1997|Hocking 1997"/> but as of 2004 this use accounts for only 13% of the market for vanillin.<ref>[[#fridge2004|FRIDGE 2004]], p. 32.</ref>

Additionally, vanillin can be used as a general purpose stain for developing [[thin layer chromatography]] (TLC) plates to aid in visualizing components of a reaction mixture.  This stain yields a range of colors for these different components.

== See also ==
*[[Phenolic compounds in wine]]

== References ==
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{{refend}}

==Notes==
<!-- See [[Wikipedia:Footnotes]] for instructions. -->
{{reflist|2}}

[[Category:Aldehydes]]
[[Category:Phenols]]
[[Category:Aromatic compounds]]
[[Category:Flavors]]
[[Category:Perfume ingredients]]
[[Category:Phenol ethers]]

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