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P1S8 Molécules organiques et couleur

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Jenny Mathiasson sur Twitter : "I've got a soft spot for stationery so here's a bit of pen-based chemistry courtesy of @compoundchem to cheer you up on a grey Monday. Enjoy! (Might be the highlight of your bank holiday weekend: HAR HAR.)… Susan Vickers sur Twitter : "Go to get some stuff laminated for #EucheMS2018 busking in our post room and end up having an brilliant conversation with the post room staff about the chemistry of glow sticks. Made my day, I love a bit of impromptu #scicomm!

Twitter. Periodic graphics: The chemistry of sunglasses | May 9, 2016 Issue - Vol. 94 Issue 19. The Chemicals Behind the Colours of Autumn Leaves. Click to enlarge With autumn looming on the horizon, the leaves on some trees have already begun the transition towards the vibrant hues of autumn. Whilst this change may outwardly seem like a simple one, the many vivid colours are a result of a range of chemical compounds, a selection of which are detailed here. Before discussing the different compounds that lead to the colours of autumn leaves, it’s worth discussing how the colours of these compounds originate in the first place.

To do this we need to examine the chemical bonds they contain – these can be either single bonds, which consist of one shared pair of electrons between adjacent atoms, or double bonds, which consist of two shared pairs of electrons between adjacent atoms. The colour causing molecules in autumn leaves contain systems of alternating double and single bonds – this is referred to as conjugation. Chlorophyll Chlorophyll is the chemical compound responsible for the usual, green colouration of most leaves. Like this: Halloween Special: The Chemistry of Blood. Click to enlarge Fake blood is an essential accessory if you’re going for a gory halloween look with your costume this year. There’s a lot of chemistry in the substance it sets out to mimic; we can explain the colour, smell, and different types of blood with the aid of chemistry (and some biology thrown in for good measure).Today’s graphic takes a look at each in turn.

The chemistry behind blood’s colour is perhaps that we’re all most familiar with. Most of us are aware that blood contains haemoglobin; this is the protein, found within red blood cells, that enables our blood to carry oxygen to our cells. It also helps carry some carbon dioxide back to the lungs, in the form of carbaminohaemoglobin, though the majority of carbon dioxide is carried in the blood as bicarbonate ions.

The red colouration of blood is due to the sub-units of the haemoglobin protein. Whereas oxygenated haemoglobin is a bright red, deoxygenated haemoglobin is a darker red colour – but not blue! Like this: Video: How to turn tomato juice into a rainbow. Pourquoi le homard change-t-il de couleur à la cuisson? TRANSFORMATION. Dans notre assiette, le homard arbore une belle couleur rouge-orangée. Pourtant, avant de passer à la casserole, la carapace de l'animal est d'un bleu sombre. Un phénomène qui titille la curiosité des scientifiques depuis des dizaines d'années, sans que ceux-ci parviennent à percer entièrement le secret de cette mystérieuse transformation.

C'est désormais chose faite ! Les chercheurs savaient déjà la carapace du homard riche en astaxanthine. Le pigment orange de sa carapace devient bleu lorsqu'il interagit avec une protéine La crustacyanine arrache des protons au pigment, entraînant son changement de couleur. THEORIES. L'attrait gastronomique pour le homard n'est pas la seule raison qui motive les scientifiques à s'intéresser à cette question.

Des verres de lunettes qui se teintent sur commande - 2 février 2015. Bientôt la fin des lunettes de soleil ? Une équipe de chercheurs du Georgia Institute of Technology vient de mettre au point des verres qui se colorent en quelques secondes à la demande du porteur, en appuyant sur un interrupteur situé sur la monture. Un concept qui vient de faire l'objet d'une publication dans la revue ACS Applied Materials & Interfaces. Plus efficace que les modèles déjà commercialisés TECHNIQUE. La lentille est constituée de quatre polymères "électrochromes", c'est-à-dire capables d'émettre une couleur lorsqu'une charge électrique est appliquée. Prototype de lunettes mis au point par l'équipe d'Anna Österholm. © American Chemical Society Des verres qui changent de couleur automatiquement, ce n'est pas un concept nouveau.

APPLICATION. The Chemistry of Bell Peppers – Colour and Aroma. Click to enlarge Bell peppers come in a range of hues, from fresh greens to vibrant reds. Chemical pigments are behind these, but what changes to cause peppers to travel through this spectrum of colours? Here we take a look at the compounds behind the colours (as well as some pepper aroma chemistry) – and find that peppers have some extraordinary chemistry to thank for some of their hues. Peppers start off green, which unsurprisingly is due to the presence of chlorophyll pigments. These are vital for photosynthesis in plants, and actually come in two subtly different forms, chlorophyll a and chlorophyll b.

All of the different colours of peppers that follow green are due to the presence of carotenoid pigments. The chemistry really starts getting interesting when we get to red peppers. Synthesis of capsanthin and capsorubin, also known as paprika ketones, requires a type of chemical reaction known as a pinacol rearrangement. Changes in colour aren’t the only effects of pepper ripening. Periodic Graphics: The Chemistry Of Pumpkins | October 12, 2015 Issue - Vol. 93 Issue 40 | Chemical & Engineering News.

Pourquoi l'autoportrait de Léonard de Vinci vieillit mal ? PORTRAIT. Ce portrait d'un homme dessiné à la craie rouge date des années 1510-15. Pour beaucoup d'experts, il constitue un autoportrait de Léonard de Vinci - même si cette thèse à ses détracteurs. Malheureusement, ce dessin a beaucoup souffert au cours des siècles et aujourd'hui, le papier présente un jaunissement généralisé. Il est aussi parsemé de taches brunes, ce qui diminue considérablement la visibilité du dessin. Un tableau soumis à rude épreuve au cours des siècles Les chromophores, ce sont de petits groupements d'atomes que l'on retrouve dans certains pigments.

L'autoportrait de Léonard de Vinci. HUMIDITÉ.