Science around us - BASF · Science around us A news service provided by BASF ... such as linalool which smells of lavender and geraniol ... aroma chemicals production at BASF

January 12, 2009 P 100/09e contact Julia Jespersen Corporate Innovation Communications phone +49 621 60-20650 fax +49 621 60-20548 [email protected]

Science around usA news service provided by BASF

BASF SE 67056 Ludwigshafen, Germany phone +49 621 60-0 fax +49 621 60-20129 http://www.basf.de e-Mail: [email protected]

In today’s world dominated by visual and acoustic sensations, the sense of smell

is often regarded as one of the “lower” senses. And yet it plays a much greater role

in our lives than is generally assumed: without it, we could neither enjoy the aromas of

an appetizing meal or wine or recognize tainted food. The saying “You really get up

my nose” also indicates how the sense of smell exerts a subliminal influence in all

our lives: it can make the difference between sympathy and antipathy and cause

long-forgotten memories to resurface.

While people can basically recognize only four different types of taste – sweet, sour,

salty and bitter – the human olfactory mucosa actually possesses about 350 different

types of olfactory receptors. The “lock and key” principle, however, dictates that

only very specific aroma molecules can dock onto these receptors and stimulate an

aroma sensation in the brain. Complex aromas simultaneously activate a large number

of receptors, greatly multiplying the number of perceivable scents. A well-trained

nose can therefore distinguish between more than 10,000 nuances of fragrance.

People surround themselves with pleasant fragrances to flatter their sense of smell.

BASF is one of the world market leaders in the field of synthetic fragrances. The core

product is citral, an aroma chemical which has been manufactured since 2004 in

Ludwigshafen in a new plant with an annual capacity of 40,000 metric tons. The

molecule consisting of ten carbon atoms (C atoms) is also responsible for the

aroma of citrus in nature, for example in citrus fruits and lemongrass. Synthetic

citral from BASF, however, not only provides the fragrance of citrus. By making

minor modifications to the molecular structure, other fragrances important for the

aroma industry can be created, such as linalool which smells of lavender and geraniol

responsible for the typical smell of roses. “These flowery fragrances are very similar

in their molecular structure. All three have an identical backbone consisting of ten

carbon atoms and, as a special feature, one oxygen atom,” explains Dr. Klaus Ebel,

Research Manager at BASF. “The critical difference is the exact position and type

of binding of the oxygen. With citral and geraniol, it is located at the end of the

carbon chain. In citral, however, it is attached by a double bond and in geraniol by

Citrus, rose and lavender – nature-identical fragrances from the chemical laboratoryS m a l l d i f f e r e n c e , b i g e f f e c t : H o w B A S F ’ s r a w m a t e r i a l c i t r a l

b e c o m e s a n e n c h a n t i n g b o u q u e t o f f r a g r a n c e s

Text, photos, i l lustrat ion and animation with sound are

avai lable at: www.basf.de/science_around_us

T h e S t o r y

Minor modifications to the molecular structure allow nature-identical fragran-ces, such as lemon, lavender and rose scents, to be produced from citral.

Photo: Elefanten

a single bond. With linalool, on the other hand, the oxygen atom is simply bound to another

carbon atom located further inside the chain”.

A small difference with a big effect: just like changing even a single indentation on a key, the three

molecules then dock onto different olfactory receptors of the nose where they induce the cor-

responding aromatic sensations. Since chemically speaking these aroma chemicals are exactly

equivalent to their natural counterparts, even the most sensitive nose will be unable to detect

the difference. BASF’s nature-identical aromas, moreover, offer two decisive advantages: firstly

their consistently high purity which is almost impossible to achieve with a natural extract.

Secondly, synthesis is often the only way of producing the required amounts of fragrance

at an acceptable price. For example, to obtain from lemongrass the 40,000 metric tons of

citral produced annually in Ludwigshafen, it would be necessary to cultivate an area of about

40,000 hectares – roughly the size of the Mediterranean island Majorca.

The technical resources required for the synthesis of citral and its related compounds, are never-

theless quite considerable. “In the citral plant in Ludwigshafen inaugurated in 2004, reaction

temperatures of up to 300 centigrade and extreme pressures of up to 300 bar are maintained

in some parts of the system. To induce the necessary chemical reactions and minimize the for-

mation of undesired by-products, we had to develop our own special catalysts with silver and

other precious metals as active components,” says Dr. Martin Schmidt-Radde, responsible for

aroma chemicals production at BASF.

Even the “marriage” of the starting materials for citral production can only be achieved under

high pressure: firstly, the relatively simple molecules isobutene (consisting of four carbon atoms)

and formaldehyde (one C atom) have to be joined together to produce the intermediates

prenol and prenal (each with five C atoms). One prenol and one prenal molecule are then

finally “married” to produce citral with its ten C atoms from which its fragrant cousins geraniol

and linalool are created in further synthesis steps. About one third of the citral produced in

Ludwigshafen, however, is used to create substances that at first appear to have little to do

with sophisticated perfumes: vitamins, or more precisely vitamins A and E as well as carotenoids

that are used as vitamin precursors and antioxidants by the metabolism. These two vitamins

have a backbone of 20 and 29 carbon atoms, and carotenoids of even 40 carbon atoms

respectively. As a result, they are of low volatility and not perceptible to the sense of smell.

Julia Jespersen Corporate Innovation Communications phone +49 621 60-20650 P 100/09e page 2





T h e P r o s p e c t s

Particularly high requirements are placed on the citral based fragrance components,

because even the tiniest aroma-relevant impurity can impair or even destroy the desired,

typical aromatic impression. Special distillation processes developed at BASF therefore

make up the final technical production step. Consistent quality is thereby assured. Now

only one hurdle remains before delivery to the customers, namely Alfred ten Haaf and his

experts from the sensory evaluation team of the Competence Center Analytics at BASF:

“The end product can be as perfect as can be in terms of analytical composition, but if

it doesn't have the right aroma, that’s the end of the line as far as release is concerned.

The customers for BASF’s aroma chemicals expect absolutely consistent aromatic

quality. Only on this basis can the fragrant composition of a perfume – consisting of a

large number of fragrance components – guarantee the expected perfume experience.

Otherwise, a fragrant disappointment is inevitable,” explains the expert. Together with his

team, the trained perfume specialist and technologist for cosmetics and detergents puts

his nose into every batch of fragrance ingredients before it is sent off to the customer. At

the end of the day, no gas chromatograph in the world can approach the sophistication of

the human nose.

To acquire a pleasant odor, creams, shampoos and detergents need only very tiny

amounts of fine aroma compounds such as citral. On the global scale, however, this

requirement adds up to huge amounts: since 2004, BASF’s existing plant in Ludwigshafen

has been producing around 40,000 metric tons of citral per year – four times the former

capacity. This makes BASF the world’s largest producer of citral and its chemical con-

geners. The main customers are cosmetic and detergent manufacturers (fragrances) and

manufacturers of food supplements and animal feedstuffs (vitamins).

Concurrently with the citral family, BASF is also developing other fragrances: one current

example is rose oxide which is part of rose fragrance and is also used as an “aroma

intensifier” for other perfumes. Since pleasantly smelling products are now taken for

granted in today’s world, fragrances are a slowly but steadily growing market unaffected

by economic cycles – because people will always be needing to bathe and wash.





T h e I n f o B o x

Links to third-party sites (“hyperlinks”) do not constitute an endorsement of such third-party sites by BASF and BASF is not responsible for the availa-bility of these sites or their contents. The hyperlinking to these sites is at the user’s own risk.




The wide world of fragrances

For centuries, perfumers had to rely exclusively on natural fragrance components,

some of which were extremely rare. The age of synthetic fragrances only began with the

manufacture of vanillin (1874) and musk (1888). In the 1930s, BASF entered the aroma

production business with phenylethyl alcohol, a nature-identical component of rose oil

with the fragrance of rosewood and rose leaves. Since the 1960s, citral has formed the

basis for the production of vitamins and aroma chemicals in Ludwigshafen.

Of the approximately 3,000 synthetically producible fragrances known worldwide, BASF

has about 100 in its portfolio – those that are economically viable to produce. Because in

many cases a fragrance is only needed in such small quantities that its synthesis – although

possible – is not worthwhile and it makes more sense to use the natural substance instead.

T h e G r a p h i c

F u r t h e r i n f o r m a t i o n c a n b e f o u n d a t :

www.aromachemicals.basf.de/ www.basf.com/group/corporate/en/content/innovations/innovation-award/2007/citral-verbund www.cphys.ruhr-uni-bochum.de/einleitung_en.htm

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Science around us - BASF · Science around us A news service provided by BASF ... such as linalool which smells of lavender and geraniol ... aroma chemicals production at BASF