10.4: Electrophilic Additions to Alkenes (2023)

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    The reactions of alkanes discussed in Chapter 4 are homolytic processes, which means that the bonds are made and broken through radical or atomic intermediates. In contrast, the \(S_\text{N}\) and \(E\) reactions of alkyl halides, considered in Chapter 8, involve heterolytic bond cleavage and ionic reagents or products. An especially important factor contributing to the differences between the reactions of the alkanes and alkyl halides is the slight ionic character of \(\ce{C-H}\) compared to \(\ce{C}\)-halide bonds (see Section 1-3). The alkenes are like the alkanes in being nonpolar compounds (Section 4-1) and it may come as a surprise that many important reactions of alkenes are heterolytic reactions. Why should this be so? No doubt because the electrons in the alkene double bonds are more exposed and accessible than the electrons in an alkane \(\ce{C-C}\) bond.

    This is evident from the atomic-orbital models of ethene described in Section 6-4C. The electrons of the double bond are pushed outward by their mutual repulsions, and their average positions are considerably farther from the bond axis than the electron positions of a single bond (Figure 10-6). In such circumstances, electrophilic reagents, which act to acquire electrons in chemical reactions (Section 8-1), are expected to be particularly reactive. This is actually the case. Furthermore, reagents that are primarily nucleophilic (electron-donating) are notoriously poor for initiating reactions at carbon-carbon double bonds. Exceptions occur when the double bonds carry substituents with a sufficiently high degree of electron-attracting power to reduce the electron density in the double bond enough to permit attack by a nucleophilic agent.

    10.4: Electrophilic Additions to Alkenes (2)

    Example of electrophilic reagents that normally add to carbon-carbon double bonds of alkenes to give saturated compounds include halogens (\(\ce{Cl_2}\), \(\ce{Br_2}\), and \(\ce{I_2}\)), hydrogen halides (\(\ce{HCl}\) and \(\ce{HBr}\)), hypohalous acids (\(\ce{HOCl}\) and \(\ce{HOBr}\)), water, and sulfuric acid:

    10.4: Electrophilic Additions to Alkenes (3)

    The mechanisms of these reactions have much in common and have been studied extensively from this point of view. They also have very considerable synthetic utility. The addition of water to alkenes (hydration) is particularly important for the preparation of a number of commercially important alcohols. Thus ethanol and 2-propanol (isopropyl alcohol) are made on a very large scale by the hydration of the corresponding alkenes (ethene and propene) using sulfuric or phosphoric acids as catalysts. The nature of this type of reaction will be described later.

    10.4: Electrophilic Additions to Alkenes (4)

    The Stepwise Ionic Mechanism, Halogen Addition

    We shall give particular attention here to the addition of bromine to alkenes because this reaction is carried out very conveniently in the laboratory and illustrates a number of important points about electrophilic addition reactions. Much of what follows applies to addition of the other halogens, except fluorine.

    A significant observation concerning bromine addition is that it and many of the other reactions listed above proceed in the dark and are not influenced by radical inhibitors. This is evidence against a radical-chain mechanism of the type involved in the halogenation of alkanes (Section 4-4D). However, it does not preclude the operation of radical-addition reactions under other conditions, and, as we shall see later in this chapter, bromine, chlorine, and many other reagents that commonly add to alkenes by ionic mechanisms also can add by radical mechanisms.

    One alternative to a radical-chain reaction for bromine addition to an alkene would be the simple four-center, one-step process shown in Figure 10-7.

    10.4: Electrophilic Additions to Alkenes (5)

    The mechanism of Figure 10-7 cannot be correct for bromine addition to alkenes in solution for two important reasons. First, notice that this mechanism requires that the two \(\ce{C-Br}\) bonds be formed on the same side of the double bond, and hence produce suprafacial addition. However, there is much evidence to show that bromine and many other reagents add to alkenes to form antarafacial addition products (Figure 10-8).

    10.4: Electrophilic Additions to Alkenes (6)

    Cyclohexene adds bromine to give trans-1,2-dibromocyclohexane:

    (Video) Addition of HBr to an alkene example

    10.4: Electrophilic Additions to Alkenes (7)

    The cis isomer is not formed at all. To give the trans isomer, the two new \(\ce{C-Br}\) bonds have to be formed on opposite sides of the double bond by antarafacial addition. But this is impossible by a one-step mechanism because the \(\ce{Br-Br}\) bond would have to stretch too far to permit the formation of both \(\ce{C-Br}\) bonds at the same time.

    The second piece of evidence against the mechanism of Figure 10-7 is that bromine addition reactions carried out in the presence of more than one nucleophilic reagent usually give mixtures of products. Thus the addition of bromine to an alkene in methanol solution containing lithium chloride leads not only to the expected dibromoalkane, but also to products resulting from attack by chloride ions and by the solvent:

    10.4: Electrophilic Additions to Alkenes (8)

    The intervention of extraneous nucleophiles suggests a stepwise mechanism in which the nucleophiles compete for a reactive intermediate formed in one of the steps.

    A somewhat oversimplified two-step mechanism that accounts for most of the foregoing facts is illustrated for the addition of bromine to ethene. [In the formation shown below, the curved arrows are not considered to have real mechanistic significance, but are used primarily to show which atoms can be regarded as nucleophilic (donate electrons) and which as electrophilic (accept electrons). The arrowheads always should be drawn to point to the atoms that are formulated as accepting a pair of electrons.]

    10.4: Electrophilic Additions to Alkenes (9)

    The first step (which involves electrophilic attack by bromine on the double bond) produces a bromide ion and a carbocation, as shown in Equation 10-1.\(^1\)

    As we know from our study of \(S_\text{N}1\) reactions (Section 8-4), carbocations react readily with nucleophilic reagents. Therefore in the second step of the bromine-addition mechanism, shown in Equation 10-2, the bromoethyl cation is expected to combine rapidly with bromide ion to give the dibromo compound. However, if other nucleophiles, such as \(\ce{Cl}^\ominus\) or \(\ce{CH_3OH}\), are present in solution, they should be able to compete with bromide ion for the cation, as in Equations 10-3 and 10-4, and mixtures of products will result:

    10.4: Electrophilic Additions to Alkenes (10)

    To account for the observation that all of these reactions result in antarafacial addition, we must conclude that the first and second steps take place from opposite sides of the double bond.

    Why Antarafacial Addition?

    The simple carbocation intermediate of Equation 10-1 does not account for formation of the antarafacial-addition product. The results with \(S_\text{N}1\) reactions (Section 8-6) and the atomic-orbital representation (see Section 6-4E) predict that the bonds to the positively charged carbon atom of a carbocation should lie in a plane. Therefore, in the second step of addition of bromine to cycloalkenes, bromide ion could attack either side of the planar positive carbon to give a mixture of cis- and trans-1,2-dibromocyclohexanes. Nonetheless, antarafacial addition occurs exclusively:

    (Video) Alkene + HBR + ROOR - Reaction Mechanism

    10.4: Electrophilic Additions to Alkenes (11)

    To account for the stereospecificity of bromine addition to alkenes, it has been suggested that in the initial electrophilic attack of bromine a cyclic intermediate is formed that has bromine bonded to both carbons of the double bond. Such a "bridged" ion is called a bromonium ion because the bromine formally carries the positive charge:

    10.4: Electrophilic Additions to Alkenes (12)

    An \(S_\text{N}2\)-type of attack of bromide ion, or other nucleophile, at carbon on the side opposite to the bridging group then results in formation of the antarafacial-addition product:

    10.4: Electrophilic Additions to Alkenes (13)

    We may seem to have contradicted ourselves because Equation 10-1 shows a carbocation to be formed in bromine addition, but Equation 10-5 suggests a bromonium ion. Actually, the formulation of intermediates in alkene addition reactions as "open" ions or as cyclic ions is a controversial matter, even after many years of study. Unfortunately, it is not possible to determine the structure of the intermediate ions by any direct physical method because, under the conditions of the reaction, the ions are so reactive that they form products more rapidly than they can be observed. However, it is possible to generate stable bromonium ions, as well as the corresponding chloronium and iodonium ions. The technique is to use low temperatures in the absence of any strong nucleophiles and to start with a 1,2-dihaloalkane and antimony pentafluoride in liquid sulfur dioxide:

    10.4: Electrophilic Additions to Alkenes (14)

    The \(\ce{C_2H_4Br}^\oplus\) ions produced in this way are relatively stable and have been shown by nmr to have the cyclic halonium ion structure.

    Complexes of Electrophilic Agents with Double Bonds

    There is a further aspect of polar additions to alkenes that we should consider, namely, that electrophilic reagents form loose complexes with the \(\pi\) electrons of the double bonds of alkenes prior to reaction by addition. Complexes of this type are called charge-transfer complexes (or \(\pi\) complexes). Formation of a complex between iodine and cyclohexene is demonstrated by the fact that iodine dissolves in cyclohexene to give a brown solution, whereas its solutions in cyclohexane are violet. The brown solution of iodine in cyclohexene slowly fades as addition occurs to give colorless trans-1,2-diiodocyclohexane.

    Precise Lewis structures cannot be written for charge-transfer complexes, but they commonly are represented as

    10.4: Electrophilic Additions to Alkenes (15)

    with the arrow denoting that electrons of the double bond are associated with the electrophile. These complexes probably represent the first stage in the formation of addition products by a sequence such as the following for bromine addition:

    (Video) Radical addition of HBr to an alkene

    10.4: Electrophilic Additions to Alkenes (16)

    Addition of Proton Acids

    We have seen that electrophiles can react with alkenes to form carbon-halogen bonds by donating positive halogen, \(\ce{Br}^\oplus\), \(\ce{Cl}^\oplus\), or \(\ce{I}^\oplus\). Likewise, carbon-hydrogen bonds can be formed by appropriately strong proton donors, which, of course, are typically strong proton acids. These acids are more effective in the absence of large amounts of water because water can compete with the alkene as a proton acceptor (also see Section 10-3E). Hydrogen chloride addition to ethene occurs by way of a proton-transfer step to give the ethyl cation and a chloride ion (Equation 10-6) followed by a step in which the nucleophilic chloride ion combines with the ethyl cation (Equation 10-7):

    10.4: Electrophilic Additions to Alkenes (17)

    All of the hydrogen halides \(\ce{HF}\), \(\ce{HCl}\), \(\ce{HBr}\), and \(\ce{HI}\)) will add to alkenes. Addition of hydrogen fluoride, while facile, is easily reversible. However, a solution of \(70\%\) anhydrous hydrogen fluoride and \(30\%\) of the weak organic base, pyridine, which is about 1/10,000 times as strong as ammonia, works better, and with cyclohexene gives fluorocyclohexane. With hydrogen iodide, care must be taken to prevent \(\ce{I_2}\) addition products resulting from iodine formed by oxidation reactions such as

    \[4 \ce{HI} + \ce{O_2} \rightarrow 2 \ce{I_2} + 2 \ce{H_2O}\]

    With hydrogen bromide, radical-chain addition may intervene unless the reaction conditions are controlled carefully (this will be discussed in Section 10-7).

    The stereochemistry of addition depends largely on the structure of the alkene, but for simple alkenes and cycloalkenes, addition occurs predominantly in an antarafacial manner. For example, hydrogen bromide reacts with 1,2-dimethylcyclohexene to give the antarafacial addition product:

    10.4: Electrophilic Additions to Alkenes (18)


    We mentioned previously that the hydration of alkenes required a strong acid as a catalyst, because water itself is too weak an acid to initiate the proton-transfer step. However, if a small amount of a strong acid such as sulfuric acid is present, hydronium ions, \(\ce{H_3O}^\oplus\), are formed in sufficient amount to protonate reasonably reactive alkenes, although by no means as effectively as does concentrated sulfuric acid. The carbocation formed then is attacked rapidly by a nucleophilic water molecule to give the alcohol as its conjugate acid,\(^2\) which regenerates hydronium ion by transferring a proton to water. The reaction sequence follows for 2-methylpropene:

    10.4: Electrophilic Additions to Alkenes (19)

    In this sequence, the acid acts as a catalyst because the hydronium ion used in the proton addition step is regenerated in the final step.

    (Video) (Organic CHEM) CH 10 Alkenes and Addition Reactions part 2

    Sulfuric acid (or phosphoric acid) is preferred as an acid catalyst for addition of water to alkenes because the conjugate base, \(\ce{HSO_4-}\) (or \(\ce{H_2PO_4-}\)), is a poor nucleophile and does not interfere in the reaction. However, if the water concentration is kept low by using concentrated acid, addition occurs to give sulfate (or phosphate) esters. The esters formed with sulfuric acid are either alkyl acid sulfates \(\ce{R-OSO_3H}\) or dialkyl sulfates \(\ce{(RO)_2SO_2}\). In fact, this is one of the major routes used in the commercial production of ethanol and 2-propanol. Ethen and sulfuric acid give ethyl hydrogen sulfate, which reacts readily with water in a second step to give ethanol:

    10.4: Electrophilic Additions to Alkenes (20)

    Aqueous versus Nonaqueous Acids. Acid Strengths

    One of the more confusing features of organic chemistry is the multitude of conditions that are used to carry out a given kind of reaction, such as the electrophilic addition of proton acids to different alkenes. Strong acids, weak acids, water, no water - Why can't there be a standard procedure? The problem is that alkenes have very different tendencies to accept protons. In the vapor phase, \(\Delta H^0\) for addition of a proton to ethene is about \(35 \: \text{kcal}\) more positive than for 2-methylpropene, and although the difference should be smaller in solution, it still would be large. Therefore we can anticipate (and we find) that a much more powerful proton donor is needed to initiate addition of an acid to ethene than to 2-methylpropene. But why not use in all cases a strong enough acid to protonate any alkene one might want to have a proton acid add to? Two reasons: First, strong acids can induce undesirable side reactions, so that one usually will try not to use a stronger acid than necessary; second, very strong acid may even prevent the desired reaction from occurring!

    In elementary chemistry, we usually deal with acids in more or less dilute aqueous solution and we think of sulfuric, hydrochloric, and nitric acids as being similarly strong because each is essentially completely disassociated in dilute water solution:

    \[\ce{HCl} + \ce{H_2O} \overset{\longrightarrow}{\leftarrow} \ce{H_3O}^\oplus + \ce{Cl}^\ominus\]

    This does not mean they actually are equally strong acids. It means only that each of the acids is sufficiently strong to donate all of its protons to water. We can say that water has a "leveling effect" on acid strengths because as long as an acid can donate its protons to water, the solution has but one acid "strength" that is determined by the \(\ce{H_3O}^\oplus\) concentration, because \(\ce{H_3O}^\oplus\) is where the protons are.

    Now, if we use poorer proton acceptors as solvent we find the proton-donating powers of various "strong" acids begin to spread out immensely. Furthermore, new things begin to happen. For example, ethene is not hydrated appreciably by dilute aqueous acid; it just is too hard to transfer a proton from hydronium ion to ethene. So we use concentrated sulfuric acid, which is strong enough to add a proton to ethene. But now we don't get hydration, because any water that is present in concentrated sulfuric acid is virtually all converted to \(\ce{H_3O}^\oplus\), which is non-nucleophilic!

    \[\ce{H_2SO_4} + \ce{H_2O} \rightarrow \ce{H_3O}^\oplus + \ce{HSO_4-}\]

    However, formation of \(\ce{H_3O}^\oplus\) leads to formation of \(\ce{HSO_4-}\), which has enough nucleophilic character to react with the \(\ce{CH_3CH_2+}\) to give ethyl hydrogen sulfate and this is formed instead of the conjugate acid of ethanol (Section 10-3E). The epitome of the use of stronger acid and weaker nucleophile is with liquid \(\ce{SO_2}\) (bp \(\sim 10^\text{o}\)) as the solvent and \(\ce{HBF_6}\) as the acid. This solvent is a very poor proton acceptor (which means that its conjugate acid is a very good proton donor) and \(\ce{SbF_6-}\) is an extremely poor nucleophile. If we add ethene to such a solution, a stable solution of \(\ce{CH_3CH_2+} \ce{SbF_6-}\) is formed. The reason is that there is no better proton acceptor present than \(\ce{CH_2=CH_2}\) and no nucleophile good enough to combine with the cation.

    A Biological Hydration Reaction

    The conversion of fumaric acid to malic acid is an important biological hydration reaction. It is one of a cycle of reactions (Krebs citric acid cycle) involved in the metabolic combustion of fuels (amino acids and carbohydrates) to \(\ce{CO_2}\) and \(\ce{H_2O}\) in a living cell.

    10.4: Electrophilic Additions to Alkenes (21)
    10.4: Electrophilic Additions to Alkenes (22)

    \(^1\)An alternative to Equation 10-1 would be to have \(\ce{Br_2}\) ionize to \(\ce{Br}^\oplus\) and \(\ce{Br}^\ominus\), with a subsequent attack of \(\ce{Br}^\oplus\) on the double bond to produce the carbocation. The fact is that energy required for such an ionization of \(\ce{Br_2}\) is prohibitively large even in water solution \(\left( \Delta H^0 \geq 80 \: \text{kcal} \right)\). One might well wonder why Equation 10-1 could possibly be more favorable. The calculated \(\Delta H^0\) for \(\ce{CH_2=CH_2} + \ce{Br_2} \rightarrow \cdot \ce{CH_2-CH_2Br} + \ce{Br} \cdot\) is \(+41 \: \text{kcal}\), which is only slightly more favorable than the \(\Delta H^0\) for \(\ce{Br_2} \rightarrow 2 \ce{Br} \cdot\) of \(46.4 \: \text{kcal}\). However, available thermochemical data suggest that the ease of transferring an electron from \(\cdot \ce{CH_2CH_2Br}\) to \(\ce{Br} \cdot\) to give \(^\oplus \ce{CH_2CH_2Br} + \ce{Br}^\ominus\) is about \(80 \: \text{kcal}\) more favorable than \(2 \ce{Br} \cdot \rightarrow \ce{Br}^\oplus + \ce{Br}^\ominus\). Thus the overall \(\Delta H^0\) of Equation 10-1 is likely to be about \(85 \: \text{kcal}\) more favorable than \(\ce{Br_2} \rightarrow \ce{Br}^\oplus + \ce{Br}^\ominus\).

    (Video) 10.3.1/10.3.2/10.3.4 Addition reactions of the alkenes

    \(^2\)The terms conjugate acid and conjugate base are very convenient to designate substances that are difficult to name simply as acids, bases, or salts. The conjugate acid of a compound \(\ce{X}\) is \(\ce{XH}^\oplus\) and the conjugate base of \(\ce{HY}\) is \(\ce{Y}^\ominus\). Thus \(\ce{H_3O}^\oplus\) is the conjugate acid of water, while \(\ce{OH}^\ominus\) is its conjugate base. Water itself is then both the conjugate base of \(\ce{H_3O}^\oplus\) and the conjugate acid of \(\ce{OH}^\ominus\)


    John D. Robert and Marjorie C. Caserio (1977) Basic Principles of Organic Chemistry, second edition. W. A. Benjamin, Inc. , Menlo Park, CA. ISBN 0-8053-8329-8. This content is copyrighted under the following conditions, "You are granted permission for individual, educational, research and non-commercial reproduction, distribution, display and performance of this work in any format."


    What is the electrophilic addition of alkenes? ›

    An electrophilic addition reaction is a reaction in which a substrate is initially attacked by an electrophile, and the overall result is the addition of one or more relatively simple molecules across a multiple bond.

    Which alkene is most reactive towards electrophilic addition reaction? ›

    A : Alkynes is more reactive than alkene towards electrophilic addition reaction.

    How many reactions do alkenes undergo? ›

    There are four major types of addition reactions that can occur with alkenes, they include: Hydogenation, Halogenation, Hydrohalogenation, and Hydration.

    What is the electrophilic addition of h2so4 to alkene? ›

    The electrophilic addition reaction between ethene and sulfuric acid. Alkenes react with concentrated sulfuric acid in the cold to produce alkyl hydrogensulphates. For example, ethene reacts to give ethyl hydrogensulphate.

    How do you identify an electrophilic addition reaction? ›

    An electrophilic addition reaction can be described as an addition reaction in which a reactant with multiple bonds as in a double or triple bond undergoes its π bond broken and two new σ bonds are formed.

    What is the rule of electrophilic addition? ›

    The electrophilic addition of HX to an alkene is said to follow Markovnikov's rule. Markovnikov's rule: During the electrophilic addition of HX to an alkene, the H adds to the carbon of the double bond with the fewest number of alkyl substitutent.

    What is the correct order of rate for electrophilic addition reaction? ›

    The correct order of reactivity towards electrophilic addition reaction : I CH 3 - C ≡ CH II CH 2 = CH 2.

    Which is the most reactive in electrophilic addition? ›

    In series of activating group OH comes first then OCH3, hence, phenol is most reactive towards electrophilic substitution reaction.

    Which is more reactive for electrophilic addition reaction? ›

    Therefore, aniline is the most reactive compound towards electrophilic aromatic substitution.

    What are the 4 reactions of alkenes? ›

    Some of the most common reactions of alkenes include addition of hydrogen (hydrogenation), addition of halogens (halogenation), addition of hydrogen halides (hydrohalogenation), and addition of water (hydration).

    Do all alkenes undergo addition reactions? ›

    Key Takeaway. Alkenes undergo addition reactions, adding such substances as hydrogen, bromine, and water across the carbon-to-carbon double bond.

    Why is electrophilic addition to alkenes important? ›

    Electrophilic addition reactions are an important class of reactions in chemistry. They hold such great value in the field of chemistry because they allow you to convert unsaturated hydrocarbons (alkene and alkynes) into another group of organic compounds such as alkanes, alcohols, alkyl halides, etc.

    Which reactions are most common in alkenes electrophilic substitution reactions? ›

    Oxidation and Polymerisation of Alkenes.

    Do alkenes undergo electrophilic reaction? ›

    Thus, alkenes prefer to undergo electrophilic addition reactions while arenes prefers electrophilic substitution reactions.

    Which of the following are examples of electrophilic addition? ›

    Here ethene is a nucleophile and Br2 is an electrophile. So addition of Br2 to ethene is an electrophilic addition reaction.

    What is an example of an alkene addition reaction? ›

    What is an example of alkene addition reactions? Alkene addition reactions include the bromine test and production of ethanol. These reactions occur through hydration, halogenation, and halohydrin reactions.

    Why does electrophilic addition occur? ›

    In organic chemistry, an electrophilic addition reaction is an addition reaction where a chemical compound containing a double or triple bond has a π bond broken, with the formation of two new σ bonds.

    What is electrophilic addition summary? ›

    Electrophilic addition is a reaction between an electrophile and nucleophile, adding to double or triple bonds. An electrophile is defined by a molecule with a tendency to react with other molecules containing a donatable pair of electrons.

    Does electrophilic mean positive or negative? ›

    Electrophiles are generally positively charged or neutral species with empty orbitals attracted to a centre rich in electrons.

    What are electrophilic reactions examples? ›

    In electrophilic aromatic substitution reactions, an atom attached to an aromatic ring is replaced with an electrophile. Examples of such reactions include aromatic nitrations, aromatic sulphonation, and Friedel-Crafts reactions.

    What is the first step of electrophilic addition? ›

    In an electrophilic addition, proton abstraction occurs first, generating a positively-charged intermediate. Nucleophilic attack is the second step.

    How do you know which molecule is most electrophilic? ›

    There are two requirements for a molecule to be considered a good electrophile. First, it must contain an electrophilic center or atom. Second, the electrophilic atom must be able to accommodate a new sigma bond.

    Which is least reactive in electrophilic substitution? ›

    Benzenesulphonic acid is least reactive in an electrophilic aromatic substitution due to −M effect.

    Which is more reactive towards electrophilic addition alkene or alkyne? ›

    (i) Alkynes are more reactive than alkenes towards electrophilic addition reaction.

    Which is more stable for electrophilic substitution reaction? ›

    There is no such structure in the intermediate for nitration of benzene, so the intermediate for toluene nitration is more stable and the reaction which goes through it is faster. We call the methy group (and alkyl groups in general) an "activating" group for electrophilic aromatic substitution.

    Which one of the following shows highest rate of electrophilic substitution reaction? ›

    Hence the correct reactivity order toward electrophilic substitution reaction is phenol>toluene>benene>nitrobenene.

    What is the order of reactivity of alkenes? ›

    So, the addition of hydrogen halide with alkene will be in order HI>HBr>HCl>HF.

    Which reaction are most common in alkenes? ›

    • The addition reaction is the most common chemical reaction that alkenes have.
    • The inclusion of additional functional groups converts a carbon-carbon double bond into a single bond in this process.

    What is the most important reaction of alkenes? ›

    The most characteristic reaction of alkenes is addition to the carbon–carbon double bond in such a way that the pi bond is broken and, in its place, sigma bonds are formed to two new atoms or groups of atoms.

    What are the first 7 alkenes? ›

    List of Alkenes
    • Propene (C3H6)
    • Butene (C4H8)
    • Pentene (C5H10)
    • Hexene (C6H12)
    • Heptene (C7H14)
    • Octene (C8H16)
    • Nonene (C9H18)
    • Decene (C10H20)

    What are the first 4 alkenes? ›

    The first four members of the alkenes are ethene, propene, butene and pentene.

    How do you solve alkenes? ›

    The general formula of alkenes is CnH2n C n H 2 n , where n represents the number of carbon atoms. Alkenes compounds normally end with the suffix "-ene". Therefore, an alkene with six carbon atoms would have the formula C6H12 C 6 H 12 .

    What is the rule addition of alkene? ›

    What is Markovnikov's Rule? When a protic acid (HX) is added to an asymmetric alkene, the acidic hydrogen attaches itself to the carbon having a greater number of hydrogen substituents whereas the halide group attaches itself to the carbon atom which has a greater number of alkyl substituents.

    Which type of reaction alkenes Cannot undergo? ›

    The answer is e) Dehydration.

    Alkenes do not undergo dehydration since there are no groups in the compound like a hydroxyl groups which can be removed as a molecule of water.

    Does electrophilic addition need a catalyst? ›

    Normally no catalyst is required in the electrophilic addition reaction of alkenes, But benzene requires a catalyst.

    What is the difference between electrophilic addition? ›

    A nucleophilic addition reaction has a nucleophile being added up. This nucleophile provides or donates electrons on the place of its addition. While an electrophilic addition reaction has an electrophile, which is an electron deficient species that accepts electrons.

    Are alkenes easily attacked by electrophilic reagents? ›

    Assertion :Alkenes are easily attacked by electrophilic reagents. Reason: Alkenes are unstable molecules in comparison to alkanes.

    Why is electrophilic substitution more reactive? ›

    Electrophilic nitration involves attack of nitronium ion on benzene ring. The reactivity of benzene ring increases with increase in the electron density on it. The group which increase the electron density on the ring also increase the reactivity towards electrophilic substitution.

    What is the addition reaction for alkenes? ›

    In an addition reaction an alkene adds elements to each of the carbons involved in the π-bond, resulting in formation of sp3 carbons from sp2 carbons. This is one of the most important types of reactions that alkenes undergo. Another important type of reaction involving alkenes is oxidative cleavage.

    What is electrophilic addition of alkynes? ›

    Alkynes undergo electrophilic addition in much the same manner as alkenes, however, the presence to two pi bonds allows for the possibly of the addition happening twice. The addition of one equivalent of hydrogen chloride or hydrogen bromide converts alkynes to haloalkenes.

    What type of reaction is alkene addition? ›

    The most common type of reaction for alkene is the addition reaction to a C=C double bond. In addition reaction, a small molecule is added to multiple bonds, and one π bond is converted to two σ bonds (unsaturation degree decreases) as a result of the addition.

    What is addition of x2 in alkene? ›

    Reaction proceed through the formation of 3- membered cyclic halonium ion. Nucleophile X− attacks from backside of cyclic halonium ion hence total reaction is anti addition reaction.

    What is addition reaction with example? ›

    Addition reactions are limited to chemical compounds that have multiple bonds, such as molecules with carbon-carbon double bonds (alkenes), with triple bonds (alkynes) or with carbonyl (C=O) groups can undergo addition as they too have double bond character. For example, CH2=CH2 + Cl2 → CH2Cl−CH2Cl.

    Why is it called electrophilic addition? ›

    An electrophilic addition reaction is an addition reaction which happens because what we think of as the "important" molecule is attacked by an electrophile. The "important" molecule has a region of high electron density which is attacked by something carrying some degree of positive charge.

    What is an example of an alkene reaction? ›

    Reactions of Alkenes
    • Hydrogenation: Addition of hydrogen.
    • Electrophilic addition reactions of alkenes.
    • Addition of hydrogen halides.
    • Halogenation: Addition of halogens.
    • Addition of Water.
    • Addition of sulfuric acid.
    • Oxidation reactions.
    • Hydroxylation: Formation of 1,2 diols.


    1. Electrophilic Addition to Alkenes-Part-2 (Addition of X2 and HOX)
    (SST Chemistry)
    2. (Organic CHEM) CH 10 Alkenes and Addition Reactions part 3
    (Chemistry Professor)
    3. Mechanism of Radical Addiiton of HBr to Alkenes in the Presence of Peroxides
    (Frostburg State University Chemistry Department)
    4. Electrophilic Addition | Reaction of Alkene (Part I) | Markovnikov's Rule | Unsaturation Test
    (Asyandi Mohd Nor)
    5. Addition of HBr to an Alkene (not symmetric)
    (Jesse Fang)
    6. Allylic/Benzylic Bromination With N-Bromo Succinimide (NBS)
    (Professor Dave Explains)


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