Selasa, 18 Desember 2012

Hoffman Product Versus Zaitsev Product In Elimination Reactions

As an organic chemistry student you will come across the topic of beta-elimination in your first semester. When performing these reactions you will often be faced with the question of where to place the carbon to carbon double bond. Do you go for the Hoffman product or the Zaitsev product in elimination reactions?

Before you can understand which products to choose, you have to understand two concepts:

Stability of Alkenes
  •     What is the Zaitsev Product
  •     What is the Hoffman Product

Stability Of Alkenes

A carbon to carbon double bond is stabilized by alkyl groups or carbon chains attached to the double bond. The more carbon groups that are attached, the more substituted the double bond will be. In other words, the greater the alkene substitution, the greater the stability of the alkene.

Thus the order of stability for substituted alkenes are as follows (assuming we are disregarding resonance possibility or conjugation)
  •     tetra-substituted = 4 groups attached
  •     tri-substituted = 3 groups attached
  •     di-substituted = 2 groups attached
  •     mono-substituted = 1 group attached
  •     non-substituted = no groups attached

These trends must be taken into account when determining which type of double bond you can and should form in your beta elimination reaction.

But how does this relate to the Zaitsev and Hoffman Products?

Zaitsev's Rule

Zaitsev's rule simply states that when you have the option to form more than one form of a double bond, you should choose the double bond that is most stable. Translating the above trends, this means you will form the more substituted double bond.

In most cases of elimination, this means that you will remove the beta-hydrogen that will give the most substituted product. This applies to any strong base that is small enough to reach this hydrogen atom, regardless of the size of the molecule.

However, this changes when you are dealing with a big and bulky base. If the base is really large, steric hindrance of the alkyl group will play a big factor. In this situation you will follow Hoffman's Rule instead

Hoffman Products

The Hoffman product in an elimination reaction is one that forms the less stable or less substituted double bond. While this is obviously not the desired product, this is the only option in certain situations. As mentioned above, a big bulky base may sometimes have a difficult time reaching the most stable hydrogen atom due to the size and bulk of the base getting in the way

When this happens, the big bulky base will reach for the most accessible hydrogen atom, usually one that is sticking out at the end of the molecule. While this forms a less stable product, it's really a choice between Hoffman or no product

To better understand the idea of a big and bulky base, picture the following scenario. Have you ever walked on the street while it was raining, next to a person carrying a huge and obnoxious umbrella? I've done it. The person under the umbrella stays nice and dry, but because of the umbrella size, everyone walking nearby has to keep at least a foot distance between themselves and the other person, as the obnoxious umbrella will keep poking you in the face if you get too close.

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Selasa, 04 Desember 2012

How to Perform Safe Body Piercing by Following Specific Guidelines

Interested to visit body piercing shops? Nowadays it's been trendier for modern youngsters to get pierced on various parts of their body. Body penetrating has been used among various aged common people ranging from babies to old men and women. Usually in the penetrating shops, the workers used to deliver set of instructions about the operations they need to perform. This will give clear thoughts and ideas about body penetrating. Piercing guns have been used as penetrating equipment to pierce body of all ages. Before involving in piercing, check whether the shop is using standardized guns to do piercing since some unsterilized guns may lead to various infections.

It's quite difficult to perform penetrating on the already pierced ear since piercing has to be done between the correct medium of space. The worker needs to be careful enough to do such operations and should make sure his hands shouldn't be shivering while piercing. Piercing is of many types which includes ear piercing, lip piercing, navel piercing and nose piercing. People have different tastes in penetrating their bodies.

Labret is one kind of penetrating that occurs below the bottom lip and above the chin. It is commonly called as 'tongue pillars'. However labret is also referred as traditional form of penetrating among American north-west coast regions. There are many types of labret takes place based on the positions of piercing in lips. Vertical labret is done on top of the bottom lip with a curved barbell. Similarly snake bites, spider bites and lowbret are the kinds of labret penetrating which takes place on different positions between lower lip and the chin.

If you are looking for body penetrating, you need to consider many facts before penetrating. Self penetrating is seriously not advisable. Even do not allow your friends to do the penetrating operation with the kit since it will lead to various dangerous problems and infections. As mentioned earlier, make sure you go for the standardized shops for piercing your body and ensure sterilized guns have been used for penetration.

While waiting in shops for piercing, have a look at the workers how they perform each and every operations for the customers and how they use every instruments for piercing. Check whether they use separate standardized instruments for each customers or not. Used or unsterilized instruments may cause several spreadable diseases. And also make sure how they interact with customers since convenience is based on interactions.

Before piercing your bodies choose the suitable jewels of correct size which will be apt for your specific body part. Make sure you buy jewels of best quality in order to avoid future infections and troubles. Have a deep research on each penetrated jewels for future use which will give you better thoughts and ideas before piercing. Hope the above said guidelines will be helpful for you to make perfect piercing on your body.

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