With alkynes are the isomeric unsaturated hydrocarbons containing two double bonds and which are kn

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With alkynes are the isomeric unsaturated hydrocarbons containing two double bonds and which are known as dienes, alkadiene and diolefins. Their general formula is therefore the same as in alkyne CnH2n-second Names diene performed similarly to alkenes, except chemical properties that, instead of continuing-EN adds continuation-diene, and it would be easier to name pronounced, before continuing diene inserted vowel (eg pentadiene instead pentdien). The position of double bonds marked with numbers that are placed in front of the names. Physical and chemical properties of this class of hydrocarbons depend on the position of the double bond in the molecule. According to the position of the double bond in the molecule (and thus to other features) within the class of diene 3 different groups or sub-classes of compounds (according to some authors, three independent class), namely: 1) KUMULOVANI Dien OR Alena 2) conjugated diene 3) isolated diene
Kumulovani dienes are those dienes wherein the double bonds are located next to each other. They are less stable than other hydrocarbons with a double bond. The main reason for the instability is the fact that this mode of binding diene probably a transitional form to the triple conjunction alkyne moving towards a carbon series due to a very stable very position. This group of diene geometric isomerism is possible. The most typical reaction Alen additions. In this group of compounds is the most common ion electrophilic addition, while the nucleophilic ion and free radical rarely.
2) conjugated diene Dienes in which two double bonds separated by one single bond called conjugated dienes. Such a system of double bonds (double-dirty-dirty-double-prime) affects the stability and properties of the compounds. In these diene is not possible geometrical isomerism although they have double bonds. Characteristic reactions of conjugated diene is 1,4-addition (if the temperature is increased to over 40 degrees Celsius), chemical properties at which the reagent chemical properties add to the ends of the conjugated system (the first and the fourth carbon atom of the system) and the double bond is transferred to the system chemical properties (between the second and third carbon atoms). In addition to these reactions conjugated dienes may enter and 1,2-addition (if the temperature is lowered to between -40 and -80 degrees Fahrenheit). Also, representatives of these groups diene come in free radical polymerization reactions (in the presence of organic peroxides). Another characteristic of conjugated systems is their greater stability (with lower energy content) compared to the corresponding diene with a different arrangement of double veza.Ove properties of conjugated diene can be explained as follows: When the alkene nehibridizovane two p orbitals overlap sideways and build π molecular orbital or π bond (two π electrons are localized chemical properties on the two carbon atoms). chemical properties When, for example, 1,3-butadiene are all carbon atoms are sp - hybridized chemical properties to each and there is one more nehibridizovana p orbitals. Lateral orbital overlap on first and second, respectively third and fourth carbon atom built two π connections. However, since the second and third carbon atom also bound σ bond it comes to the p orbitals overlap between them. This creates a cloud of electrons π 4 located above and below the plane of butadiene; π electrons are localized to specific carbon atoms (such as alkenes), but all four π electrons under the influence of all four carbon atoms (delocalized are). All this contributes to the stability chemical properties of the 1,3-butadiene, and additions may be made to the ends of the system, chemical properties ie in 1,4 position. Typical 1,4-addition of conjugated diene has great practical significance since it allows to thereby obtain different compounds; for example, by polymerizing chemical properties conjugated diene produces synthetic rubber. 3) isolated diene isolated dienes they dienes in which the two double bonds separated (distant) from each other by at least two single bonds (ie with a single sp hybridized chemical properties carbon atom). Dienes with isolated double bonds to behave in chemical terms as well as alkenes, chemical properties which means that it will enter the same chemical reactions and alkenes. Two connections are distant from each other and react independently of the other, and this first one, then the other. That's why we say that this group diene has two functional parts of the molecule. In particular the diene group of the possible geometrical (cis-trans) isomerism. Simplest compound from this group diene is 1,4-pentadiene.
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