Our modern society is based to a large degree on the chemicals we discuss in this chapter. Introduction of a halogen into a molecule chlorination, bromination general reaction. Combustion the combustion of carbon compounds, especially hydrocarbons, has been. In other words, an alkane consists of hydrogen and carbon atoms arranged in a tree structure in which all the carboncarbon bonds are single. Applying heat and a catalyst can crack larger, more complex alkanes and produce smaller, more useful alkanes and alkenes. Organic chemistry science at yorkdale with jessica. These reactions are employed to illustrate how we can predict and use energy changesparticularly ah, the heat evolved or absorbed by a reacting system, which often can be estimated from bond ener. The reaction uses h2 and a precious metal catalyst. Alkanes when we combine the two high bond enthalpy and being nonpolar this makes alkanes quite unreactive alkanes dont react with acidsbases or oxidizing agents this is a useful trait and alkanes are used as lubricating agents and the backbone of polymers but when the do react.
By reduction of alkyl halides rx haloalkanes rx when heated with reducing agents like. Ch08 reacns of alkenes landscape page 1 reactions of alkenes since bonds are stronger than bonds, double bonds tend to react to convert the double bond into bonds this is an addition reaction. Alkanes are stable compounds and are generally unreactive. Reactions of alkanes combustion of alkanes oxidation and reduction reaction halogenationsubstitution reaction 1 conti in a chemical reaction. Hydrocarbons are further divided into several structural types called, alkanes, alkenes. Metathesis of alkanes and related reactions accounts of.
In organic chemistry, an alkane, or paraffin a historical name that also has other meanings, is an acyclic saturated hydrocarbon. In this context, saturated means that each carbon has the maximum number of hydrogens bonded to it. Preparations alkenes are generally prepared through. Synthesis 2 reactions of alkanes master organic chemistry. Preparations include the dehydration of alcohols, the dehydrohalogenation of alkyl halides, and. The reactions between alkanes and chlorine or bromine there is no reaction in the dark. The catalysts is not soluble in the reaction media, thus this. The order and relative rates of the various bondbreaking and bondforming steps.
The transformation of alkanes remains a difficult challenge because of the relative inertness of the c. Alkane complexes have received special attention within the organometallic community because of their potential intermediacy in alkane activation reactions. Some important substitution reactions of alkanes are discussed below. Number core chain from an end nearest a substituent 3. Alkanes are rarely prepared from other types of compounds because of economic reasons.
The halogen reaction is very important in organic chemistry because it opens a gateway to further. Well be learning about different aspects of molecular structure, including common functional groups and conformations. The properties of organic molecules depend on the structure, and knowing the names of organic compounds allow us to communicate with other chemists. Alkanes are not very reactive when compared with other chemical species.
The rewards for asserting synthetic control over unfunctionalized, saturated hydrocarbons are considerable, however, because converting short alkanes into longer chain analogues is usually a valueadding process. Ppt reactions of alkanes powerpoint presentation free. Despite their relative inertness, alkanes undergo several important reactions that are discussed in the following section. Reactions of alkenes chapter 6 2 a reaction mechanism describes how a reaction occurs and explains the following. The tail of the arrow starts at the initial position of the electron pair at an atom for a lone pair. Organic chemistry university of california riverside. Alkanes, cycloalkanes, and functional groups khan academy.
Reactions of alkanes 1 chapter 9 reactions of alkanes radicals irene lee case western reserve university 2 no transcript 3 alkanes are very unreactive compounds because they have only strong s bonds and atoms with no partial charges 4 reaction of alkane with cl2 or br2 5 factors that determine product distribution. Addition of h2 across the pbond of an alkene to give an alkane. Alkane names, formulas, properties memorize sections. These reactions include free radical halogenations of alkanes and free radical additions to alkenes. Alkanes the most basic of all organic compounds undergo very few reactions. Which bonds are broken and which new ones are formed. In substitution reactions, a hydrogen of a hydrocarbon is replaced by an atom or a. Butane boils at about 0oc, which is why butane lighters do not function well below that temperature. Find materials for this course in the pages linked along the left. It is possible to force the equilibrium to the right alkene by removing one or both of the products. Halogenation of an alkane is carried out by treating it with a suitable halogen in presence of ultraviolet light or by heating the reaction mixture to 520. However, ignoring financial considerations, alkanes can be prepared from the following compounds. Lets summarize the reactions of alkanes and build a reaction map. Other types of reaction have been substitution and elimination.
Janice gorzynski smith university of hawaii chapter 4 alkanes. This section deals with wurtz reaction,frankland reaction. Most chemical reactions require a functional group. This is because the cc bond and the ch bond are relatively strong. Alkanes, because of having only cc and ch sigma bonds undergo only substitution reactions. Preparation of alkanes from unsaturated hydrocarbons. Reactions of alkenes university of texas at austin. General methods of preparation of alkanes wurtz reaction. The reactions of saturated hydrocarbons and compounds modelling them with metal complexes, leading to the cleavage of the. For making models of alkanes, you can use toothpicks for bonds and plasticine balls for atoms. Physical properties of alkanes comparison of boiling points for alkanes and alcohols compound b. Reactions of alkanes, radicals ebooks, academic notes. Both of these reactions are oxidationreduction reactions.
In substitution reactions, a hydrogen of a hydrocarbon is replaced by an atom or a group of atoms. Can conditions be found in which the reaction will take place at a practical rate. Learn the iupac system for naming alkanes and cycloalkanes. The reaction between alkanes and iodine iodine doesnt react with the alkanes to any extent at least, under normal lab conditions. The most important application of alkanes is in oxidation reactions. Lecture handouts organic chemistry i chemistry mit. The parent alkane is the longest continuous chain that contains the double bond. The alkanes and cycloalkanes, with the exception of cyclopropane, are probably the least chemically reactive class of organic compounds. In the presence of a flame, the reactions are rather like the fluorine one producing a mixture of carbon and the hydrogen. The two reactions of more importaces is combustion and halogenation, i. This reaction is known as wurtz reaction and used for the preparation of symmetrical alkanes. They are named as derivatives of alkanes with the suffix ane changed to ene. The clemmensen reaction can be used to reducing an aryl ketone which is the product of a friedelcrafts acylation. However, they undergo the following reactions under certain conditions.
Chemical properties of alkanes chemistry libretexts. Pdf reactions of alkanes combustion of alkanes oxidation and. The 3d representations and ballandstick models for these alkanes indicate the. Alkanes are less dense than water and swim on top of water 2. This reaction is known as wurtz reaction and is used for the preparation of higher alkanes containing even number of carbon atoms. To me it appears like a primeval tropical forest full of the most remarkable things, a dreadful endless jungle into which one does not dare enter, for there seems to be no way out. Petroleum and natural gas are the major sources of aliphatic hydrocarbon while coal is an important source of aromatic hydrocarbons. Unsaturated hydrocarbons alkenes and alkynes react with h 2 in the presence of finely divided catalysts such as platinum, palladium or nickel to form alkanes. In the presence of certain catalysts called initiators, many alkenes form polymers by the addition of monomers greek. The alkanes range in complexity from the simplest case of methane. The letter in brackets, x, designates the type of reaction mechanism. Antimarkovnikov addition used when an alkene should be converted into an alcohol via antimarkovnikovs rule.
In general, alkanes do not react with many reagents. The important fuels like petrol, kerosene, coal gas, cng, lpg etc. For each electron pair either a bonding pair or lone pair that changes position in a reaction, one arrow is required. An introduction alkanes are aliphatic hydrocarbons having onl. Dehydration reactions of alcohols dehydration of alcohols requires an acidic catalyst to convert the hydroxyl into a good leaving group this is an equilibrium reaction. B halogenation halogenation a substitution reaction. Elimination reactions alkenes alkenes contain a carboncarbon double bond. Chapter reactions of alkanes, radicals 1 explain why alkanes are generally considered unreactive compounds. Fgs behave similarly in every molecule they are part of. General methods of preparation of alkanes is the topic which has a potential of fetching a question in iit jee and jee mainadvanced examination very frequently. Organocuprates gilman reagents couple with alkyl halides to provide alkanes. Download in free pdf hydrocarbons are composed of carbon and hydrogen.
Substitution reactions of alkanes reaction of alkanes with bromine chlorine in uv light in the presence of uv light alkanes react with chlorine to form a mixture of products with the halogens substituting hydrogen atoms. These reactions are employed to illustrate how we can predict and use energy changesparticularly ah, the heat evolved or absorbed by a reacting system, which often can be. Addition of zinc amalgam, znhg and acid to a ketone results in an alkane. We often refer to alkanes as aliphatic hydrocarbons, because the physi cal properties of the higher members of this class resemble those of the long carbonchain. Alkanes 2 organic chemistry nowadays almost drives me mad. In addition to carbon dioxide, water and heat a variety of. Alkanes and cycloalkanes 11 million organic compounds which are classified into families according to structure and reactivity functional group fg.
This reaction is used industrially to prepare alkyl halides more in chapter 15. This is because the backbone carbon atoms in alkanes have attained their octet of electrons through forming four covalent bonds the maximum allowed number of bonds under the octet rule. Clemmensen reduction to alkanes clemmensen reduction to alkanes definition. For alkenes, alkynes and aromatic hydrocarbons, spring models can be constructed.
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