Sunscreens

  

    Sunscreen (also commonly known as sun screen, sunblock, suntan lotion, sunburn cream, sun cream or block out) is a lotion, spray, gel or other topical product that absorbs or reflects some of the sun's ultraviolet (UV) radiation on the skin exposed to sunlight and thus helps protect against sunburn. Skin-lightening products have sunscreen to protect lightened skin because light skin is more susceptible to sun damage than darker skin. A number of sunscreens have tanning powder to help the skin to darken or tan; however, tanning powder does not provide protection from UV rays. Depending on the mode of action, sunscreens can be classified into physical sunscreens (i.e., those that reflect the sunlight) or chemical sunscreens (i.e., those that absorb the UV light).

  

  The use of sunscreens in recent years has increased due to heightened concern over the risk of skin cancer and other conditions caused b

y exposure to UV radiation. in DNA, for example, UV radiation can cause adjacent thymine bases to form mutagenic dimers. Sunscreens afford protection from radiation because they contain aromatic molecules that absorb energy in the UV region of the electromagnetic spectrum. Absorption of UV radiation by these molecules promotes π and nonbonding electrons to higher energy levels, after which the energy is dissipated by relaxation through molecular vibration. In essence, the UV radiation is converted to heat (IR radiation).

  

  Sunscreens are classified according to the portion of the UV spectrum where their maximum absorption occurs. Three regions of the UV spectrum are typically discussed. The region from 320 to 400 nm is called UV-A, the region from 280 to 320 nm is called UV-B, and the region from 100 to 280 nm is called UV-C. the UV-C region is potentially the most dangerous because it encompasses the shortest UV wavelengths and is therefore of the highest energy. However, ozone and other components in Earth’s atmosphere absorb UV-C wavelengths, and thus we are protected from radiation in this part of the spectrum so long as earth’s atmosphere is not compromised further by ozone-B radiation passes through the atmosphere to reach us, and it is against these regions of the spectrum that sunscreens are formulated. Tanning and sunburn are caused by UV-B radiation. Risk of skin cancer is primarily associated with UV-A radiation, although some UV-A wavelengths may be important as well.

   The specific range of protection provided by a sunscreen depends on the structure of its UV-absorbing groups. Most sunscreens have structures derived from the following parent compounds: p-aminoibenzoic acid (PABA), cinnamic acid (3-phenylpropenoic acid), benzophenone (diphenyl ketone), and salicylic acid (o-hydroxybenzoic acid). The structures and λmax for a few of the most common sunscreen agents are given below. The common theme among them is an aromatic core in conjugation with other functional groups.

octyl 4-N,N-dimethylaminobenzoate

2-Ethylhexyl 4-methoxycinnamate

2-Hydroxy-4-methoxybenzophenone

Ethanol as a Biofuel

   

   Ethanol is said to be a renewable energy source because it can be made by the action of microorganisms and enzymes through fermentation of grains and other agricultural sources such as switchgrass and sugarcane. The crops themselves grow, of course, by converting light energy form the sun to chemical energy through photosynthesis. Once obtained, the ethanol can be combined with gasoline in varying proportions and used in internal combustion engines.  During the year 2007, the United States led the world in ethanol production with 6.5 billion U.S.gallons, followed closely by Brazil with 5 billion gallons.

  Biobutanol,which is also called as biogasoline, is often claimed to provide a direct replacement for gasoline, because it can be used directly in a gasoline engines.When used as a replacement for gasoline, ethanol has a lower energy content, by about 34% per unit volume. This and other factors such as costs in energy required to produce the agricultural feedstock, especially corn, have created doubts about the wisdom of an ethanol-based program as a renewable energy source. Production of ethanol from corn is 5 to 6 times less efficient than producing it from sugarcane, and it also diverts production of a food crop into an energy source. World food shortages may be a result.

  Actually, a biofuel is a fuel that is derived from biological materials, such as plants and animals. Also biofuel can still be seen as fuel derived from organic matter (obtained directly from plants, or indirectly from agricultural, commercial, domestic, and/or industrial wastes).Examples of this carbon fixation occur in plants and microalgae through the process of photosynthesis. These fuels are made by a biomass conversion (biomass refers to recently living organisms, most often referring to plants or plant-derived materials). This biomass can be converted to convenient energy containing substances in three different ways: thermal conversion, chemical conversion, and biochemical conversion. This biomass conversion can result in fuel in solid, liquid, or gas form. This new biomass can be used for biofuels. Biofuels have increased in popularity because of rising oil prices and the need for energy security.

  Bioethanol is an alcohol made by fermentation, mostly from carbohydrates produced in sugar or starch crops such as corn, sugarcane, or sweet sorghum. Cellulosic biomass, derived from non-food sources, such as trees and grasses, is also being developed as a feedstock for ethanol production. Ethanol can be used as a fuel for vehicles in its pure form, but it is usually used as a gasoline additive to increase octane and improve vehicle emissions. Bioethanol is widely used in the USA and in Brazil. Current plant design does not provide for converting the lignin portion of plant raw materials to fuel components by fermentation.

Organic Chemistry: Perfume

  Perfumes using aldehydes may be floral, fruity or citrus in nature. Fatty aldehydes contain long chains of carbon atoms connected to an aldehyde group. They have 8-13 carbon atoms in their molecular formula. The fatty aldehydes have a very pleasant odor, with a fruity or a floral scent, and can be detected in very low concentrations.Fresh floral aldehyde adds the impression of fresh breezes and flowers like jasmine, rose, iris and lily of the valley. Because of these characteristics, the fatty aldehydes are used in the formulation of many perfumes. They are also added to soaps and detergents to give them their "fresh lemon scent." Green floral aldehydes give perfumes sharper notes and aromas of the outdoors. The result is a fragrance with the scent of green grass and plants.  While Woody floral aldehyde adds the scents of cedar, patchouli, oak and other wooden tones that suggest warmth.

  The aromatic aldehydes have a benzene or phenyl ring connected to the aldehyde group. The aromatic aldehyde molecules have very complex structures but are probably the easiest to identify. Benzaldehyde is an example which is the simplest aromatic aldehyde consisting of Benzene ring with a formyl substituent and has pleasant almond-like odor. Cinnamaldehyde/ 3-phenyl-2-propenal is of complex structure that gives cinnamon note. Vanillin/4- hydroxy-3-methoxy-benzaldehyde is used as vanilla note, an ubiquitous note in almost all fragrances. Anisaldehyde or anisic aldehyde is widely used for its good tenacity. It is the main component for numerous floral accords like lilac, hawthorn, anise, honeysuckle etc.

  Most widely used aldehydes in perfumery are C7 (possessing a herbaceous green aroma), C8 (octanal, orange-like), C9  (smelling of roses), C10 (decanal, powerfully evocative of orange rind), Citral, a complex 10-carbon aldehyde (fragrance of lemons), C11 (undecanal, “clean” aldehydic, naturally present in coriander leaf oil~also used is unsaturated C11 undecen-1-al), C12 (the odor of lilacs or violets), C13 (waxy, with grapefruit tone)and the C14  (evoking the scent of peach-skin).

 SOME ALDEHYDIC FRAGRANCES:

Apres L'Ondee (1906), is said to be the First Fragrance to use Anisic Aldehyde.

Before Chanel No. 5, which is said to be the first modern aldehydic fragrance developed by Ernest Beaux in 1921 and officially launched in 1922 for sale. Coco Chanel had commisseioned him to create something with modern innovations and he came up with aldehydes. But before that, fragrance houses like L.T Piver and Houbignat had been successfully producing fragrances with aldehydes.

Chanel No. 5 (and later, No. 22) used a bouquet of aliphatic - or "fatty" - aldehydes (C10, C11, and C12) that together combine to produce a crisp citrus-and-floral note, with a pronounced soapy tone.

   

  You might also like to try some of the popular aldehydic fragrances: Lanvin Arpege, Jean Patou Joy,Ivoire de Balmain, Chloe, Yves Saint Laurent Rive Gauche, Elizabeth Taylor White Diamonds, Givenchy Ysatis, Dior Miss Dior, Estee Lauder Knowing, Guerlain Vol de Nuit, Avon Rare Gold, Joop! Femme, Tommy Hilfiger True Star, Givenchy L'Interdit, Agent Provocateur Maîtresse, Dolce & Gabbana Classique, and Lagerfeld Femme.