J&J+(Juan+and+Jon)

PROPERTIES OF ALKANES

 * 1) ====Homologous Series: A series of organic compounds that have similar structural features but differ from adjacent members by group. Basically they are a group of chemicals with the same general formula. ====
 * 2) ====Boiling points for a homologous series should increase as you go up the chain because of the increasing molar mass. However the increase get’s smaller and smaller as you go up the chain because the percentage increase in molar mass also decreases. ====
 * 3) ====  Isomers are compounds with the same molecular formula but different structural formula. An example would be Butane and isobutane versions of C 4 H 10. Another example would be pentane, 2-methylbutane and 2,2-dimethylpropane all having C 5 H 12 .  ====
 * 4) ====The more spherical the structure of an isomer, the lower the boiling point because there will be less surface area to form intermolecular forces. The isomers of pentane would be arranged pentane, 2-methylbutane and 2,2-methylbutane in descending order. The strucutre get’s more and more spherical therefore the boiling point gets lower. ====

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Introduction:
====Alkanes are chemical compounds that consist of the elements Carbon (C) and Hydrogen (H) linked together by single bonds. Since the alkanes are made of single bonds, they are saturated. This saturation makes alkanes less reactive, and therefore, their reactivity is considered low. To get a reaction, an energy input is needed such as a high temperature.====

====We can attribute the low reaction of Alkanes to two things. First is its singular bond. THis bond is short and very strong, hence it will be hard to break this bond and have the elements react with it. Second is its polarity. It does not have any, so this means that the attraction of the Alkanes is evenly distributed to each other, allowing an equal amount of pull, for a stronger bond.====

====C ombustion is the production of heat and sometimes light when there is a chemical reaction between a fuel and an oxidant. This will give an exothermic reaction which in turn produces heat. Complete combustion uses up all the fuel in a reaction and produces a limited number of products. Incomplete combustion occurs when there is not enough of an oxidant to burn up all the fuel in an efficient manner. ====

==== In incomplete combustion, the products formed will be that of complete combustion and other products. For instance, a hydrocarbon burning with perfect efficiency in air produces carbon dioxide and water as by-products. If it burns with imperfect efficiency or undergoes an incomplete combustion, it will produce carbon monoxide and things like nitrogen oxides. ====

==== It is much more likely for combustion to be incomplete than for it to be complete, particularly with solid fuels, because of the inherent difficulty of getting oxygen to a combusting fuel quickly. Incomplete combustion produces the by-products that are considered pollutants. ====

- So that the final product is stable with no unpaired electrons
====   ====  Alkenes are a family of hydrocarbons (compounds containing carbon and hydrogen only) containing a carbon-carbon double bond. The first two are:  You can work out the formula of any of them using: **CnH2n** The table is limited to the first two, because after that there are isomers which affect the names. code
 * What are alkenes?**
 * Formulae**
 * ethene || C2H4  ||
 * propene || C3H6  ||

code All the alkenes with 4 or more carbon atoms in them show**//structural isomerism//**. This means that there are two or more different structural formulae that you can draw for each molecular formula. For example, with C4H8, it isn't too difficult to come up with these three structural isomers:
 * Isomerism in the alkenes**
 * //Structural isomerism//**

**Boiling Points** The boiling point of each alkene is very similar to that of the alkane with the same number of carbon atoms. Ethene, propene and the various butenes are gases at room temperature. All the rest that you are likely to come across are liquids. In each case, the alkene has a boiling point which is a small number of degrees lower than the corresponding alkane. The only attractions involved are Van der Waals dispersion forces, and these depend on the shape of the molecule and the number of electrons it contains. Each alkene has 2 fewer electrons than the alkane with the same number of carbons. ||
 * **Physical properties of the alkenes**
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You will find the boiling points of the alkanes explained in some detail on the [|introductory alkanes page]. Everything said there applies equally to the alkenes. You will find the way [|geometric isomerism] affects melting and boiling points explained towards the bottom of the page you get to by following this link. <span style="font-family: Helvetica,Arial;">Use the BACK button on your browser to return to this page.
 * Note:** If you aren't sure about [|Van der Waals forces], then you should follow this link before you go on.

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code Alkenes are virtually insoluble in water, but dissolve in organic solvents. ||
 * Solubility**
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<span style="font-family: Helvetica,Arial;">Use the BACK button on your browser to return to this page.
 * Note:** The reasons for this are exactly the same as for the alkanes. You will find a detailed explanation on the[|introductory alkanes page.]

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code <span style="font-family: Helvetica,Arial;">**Chemical Reactivity** <span style="font-family: Helvetica,Arial;">**Bonding in the alkenes** We just need to look at ethene, because what is true of C=C in ethene will be equally true of C=C in more complicated alkenes. Ethene is often modelled like this: The double bond between the carbon atoms is, of course, two pairs of shared electrons. What the diagram doesn't show is that the two pairs aren't the same as each other. One of the pairs of electrons is held on the line between the two carbon nuclei as you would expect, but the other is held in a molecular orbital above and below the plane of the molecule. A molecular orbital is a region of space within the molecule where there is a high probability of finding a particular pair of electrons. In this diagram, the line between the two carbon atoms represents a normal bond - the pair of shared electrons lies in a molecular orbital on the line between the two nuclei where you would expect them to be. This sort of bond is called a sigma bond. The other pair of electrons is found somewhere in the shaded part above and below the plane of the molecule. This bond is called a pi bond. The electrons in the pi bond are free to move around //anywhere// in this shaded region and can move freely from one half to the other. ||
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 * Note:** This diagram shows a side view of an ethene molecule. The dotted lines to two of the hydrogens show bonds going back into the screen or paper away from you. The wedge shapes show bonds coming out towards you.
 * <span style="font-family: Arial,Helvetica;">The pi electrons are not as fully under the control of the carbon nuclei as the electrons in the sigma bond and, because they lie exposed above and below the rest of the molecule, they are relatively open to attack by other things.
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If you //do// need to know about the [|bonding in ethene] in detail, follow this link as well. <span style="font-family: Helvetica,Arial;">Use the BACK button on your browser to return to this page.
 * Note:** Check your syllabus to see if you need to know how a pi bond is formed. If you are studying a UK-based syllabus and haven't got a copy of that [|syllabus], find out how to get one by following this link.

|| Like any other hydrocarbons, alkenes burn in air or oxygen, but these reactions are unimportant. Alkenes are too valuable to waste in this way. The important reactions all centre around the double bond. Typically, the pi bond breaks and the electrons from it are used to join the two carbon atoms to other things. Alkenes undergo**//addition reactions//**. For example, using a general molecule X-Y. . . The rather exposed electrons in the pi bond are particularly open to attack by things which carry some degree of positive charge. These are called **//electrophiles//**. If you explore the rest of the alkene menu, you will find lots of examples of this kind. ||
 * <span style="font-family: Arial,Helvetica;">**The reactions of alkenes**
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<span style="font-family: Helvetica,Arial;">In fact, if you are //only// really interested in mechanisms, then look at that page and then explore the rest of the electrophilic addition menu in the mechanisms section of this site. ||
 * Note:** If you need to know about organic reaction mechanisms, it would be a good idea to read the page explaining the background to [|electrophilic addition] before you start looking at individual cases from the alkenes menu.

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==== <span class="author-g-5mx0fx32r4kpmq8p url" style="background-color: #ffc7f1; cursor: auto; padding-bottom: 1px; padding-top: 1px;"><span style="cursor: pointer !important;">[]  ==== ==== <span class="author-g-5mx0fx32r4kpmq8p url" style="background-color: #ffc7f1; cursor: auto; padding-bottom: 1px; padding-top: 1px;"><span style="cursor: pointer !important;">[|http://www.docbrown.info/page06/OrgMechs.htm] <span class="author-g-5mx0fx32r4kpmq8p padtag padtag_ALKANES url" style="background-color: #ffc7f1; cursor: auto; padding-bottom: 1px; padding-top: 1px;"><span style="border-bottom-color: #606060; border-bottom-left-radius: 3pt 3pt; border-bottom-right-radius: 3pt 3pt; border-left-color: #8c8c8c; border-right-color: #707070; border-style: solid; border-top-color: #9c9c9c; border-top-left-radius: 3pt 3pt; border-top-right-radius: 3pt 3pt; border-width: 1px; color: #2e2eaa !important; cursor: pointer !important; padding-left: 2pt; padding-right: 2pt; text-decoration: none !important;"> [|#ALKANES]   ==== <span class="author-g-5mx0fx32r4kpmq8p padtag padtag_ALKANES url" style="background-color: #ffc7f1; cursor: auto; padding-bottom: 1px; padding-top: 1px;"><span style="border-bottom-color: #606060; border-bottom-left-radius: 3pt 3pt; border-bottom-right-radius: 3pt 3pt; border-left-color: #8c8c8c; border-right-color: #707070; border-style: solid; border-top-color: #9c9c9c; border-top-left-radius: 3pt 3pt; border-top-right-radius: 3pt 3pt; border-width: 1px; color: #2e2eaa !important; cursor: pointer !important; padding-left: 2pt; padding-right: 2pt; text-decoration: none !important;">http://www.chemguide.co.uk/organicprops/alkenes/background.html