Alkenes and Dienes – Organic Chemistry – list of solved problems

Go to the page with the solutions to the problems.

Alkenes and Dienes – problem list

Problem 1)

The addition of hydrogen to 1-methylcyclohexene leads to the formation of a single product, in the presence of palladium on carbon. Justify the result.

Problem 2)

What will be the major product obtained on addition of HBr over 2-methylbut-1-ene?

Problem 3)

Compare the result of the reaction of bromine in CCl4 with the E and Z isomers of but-2-ene.

Problem 4)

Addition of borane in THF followed by hydrogen peroxide in basic medium of 1-methylcyclohexene leads to the formation of a mixture of enantiomers. Draw their structures.

Problem 5)

Justify the order of reactivity of the following alkenes against acid catalyzed hydration reactions:


Problem 6)

Complete the following scheme:


Problem 7)

Write the fitted equations to perform the following transformations:

  • a) propene  →  1-bromopropane.
  • b) propene  →  2-chloropropane
  • c) propene  →  propan-1,2-diol
  • d) propene  →  propane-2-ol
  • e) but-2-ene  →  acetic acid
  • f) styrene  →  benzaldehyde

Problem 8)

Complete the scheme (A-F), identifying the following species (radical initiator, reductant, electrophile, nucleophile, and oxidant) for the reactions described. Also, indicate whether the process follows Markovnikov’s rule and whether the stereoselectivity is syn or anti.


Problem 9)

Choose the starting olefin (I-III) to prepare each of the compounds (A-F) and describe the reagents and reaction conditions you consider necessary for each case.


Problem 10)

Indicate in a reasoned way if the following statements are true or false:

  • a) The addition of hydrogen halides to alkenes always gives the Markovnikov addition product.
  • b) Ozonolysis of an alkene produces two carbonyl compounds.
  • c) Acid-catalyzed hydration of alkenes has syn stereochemistry.
  • d) The addition of halogens to alkenes and the formation of halohydrins are anti additions.

Problem 11)

Draw the major product (A-F) obtained in each of the following reactions (a-f):


Problem 12)

Justify the following result by considering the reaction mechanism:


Problem 13)

Complete the following scheme:


Problem 14)

What products would be obtained in the ozonolysis of the following alkenes?


Problem 15)

Draw the structures of the 1,2 and 1,4 addition products of the following dienes with Br2 and H3O+.


Problem 16)

Predict the major product obtained in the Diels-Alder reaction of the following dienes with the dienophiles given.


Problem 17)

Using as starting product any of the olefins (I-III),


describe the procedures to obtain:

  • a) a primary haloalkane
  • b) a secondary haloalkane
  • c) a cyclic ketone
  • d) a dialdehyde
  • e) a haloalkene
  • f) cyclopentane
  • g) propanedioic acid

Problem 18)

Describe the reagents needed to perform the following transformations:


Problem 19)

Describe the process of formation of a trimer from 2-methylpropene by treatment with BF3 and traces of water in methylene chloride at low temperature.

Problem 20)

Justify the experimental results (relative rate of epoxidation of alkenes) described in the following table:

alkene relative rate
CH2=CH2 1
CH3CH=CH2 22
(CH3)2C=CH2 484
(CH3)2C=CHCH3 6526

Problem 21)

The following reagents (indicated in the table) are used for various reactions on alkenes. Identify in which reactions they participate and which one acts as an electrophile, nucleophile, oxidant or reductant.

HBr / peroxides

Problem 22)

Draw the structure of the product(s) obtained from cyclopentene with the following reagents, taking into account the stereochemistry of the process:

  • a) 1) H2SO4; 2) H2O
  • b) CHCl3 / t-BuOK
  • c) HBr / peroxides
  • d) HBr
  • e) Br2
  • f) Cl2 / H2O
  • g) H2O / H3PO4
  • h) R-COOOH

Problem 23)

Complete the following reaction:


Problem 24)

Describe the stereochemistry of the product/s obtained on the addition of chlorine to (E)-hex-3-ene.

Problem 25)

Choose the appropriate starting product (I or II), to obtain the following compounds (A-D).


Problem 26)

Relate the following concepts (a-d) to the reactions (I-IV) described below:

  • a) Markovnikov addition I) mercuriation / demercuriation
  • b) stereospecific process II) hydration of alcohols
  • c) anti addition III) catalytic hydrogenation
  • d) anti-Markovnikov addition IV) hydroboration / oxidation

Problem 27)

State the products of bromine addition on cyclopentene and methylcyclohexane, paying special attention to stereochemistry.

Problem 28)

Describe the stereoisomers obtained in the reaction of formation of halohydrins with a mixture of (E)- and (Z)-pent-2-ene.

Problem 29)

Draw the structures of the products obtained from the reaction with diazomethane of:

  • a) cycloheptene
  • b) 1-methylcyclohexene
  • c) (E)-but-2-ene

Problem 30)

Describe the products obtained by treatment with a peracid of:

  • a) 1,2-dimethylcyclohexene
  • b) 2-methylbut-2-ene
  • c) 2-methylpropene
  • d) cyclohexa-1,4-diene

Problem 31)

The Z– and E-isomers of hex-2-ene react independently by:

  • a) catalytic hydrogenation
  • b) electrophilic addition of HBr
  • c) epoxidation
  • d) ozonolysis

Deduce which reactions give the same compound from both isomers.

Problem 32)

Draw and clearly indicate the stereochemistry of the compounds obtained from the addition of 1 mol of bromine on alkenes I-IV.


Problem 33)

The oxidative cleavage with permanganate in basic medium, followed by treatment with an acid, of a series of alkenes leads to the formation of the following fragments (a-f). Identify what would be the starting products for each of the cases.


Problem 34)

Determine the structure of a hydrocarbon of molecular formula C8H14 which gives by catalytic hydrogenation a compound of molecular formula C8H18. Ozonolysis of said compound leads to the formation of acetaldehyde, acetone and propanedial. Draw the three possible constitutional isomers obtained when said hydrocarbon is treated with 1 mol of HCl.

Problem 35)

Draw the structure of the dimers resulting from the treatment of the following alkenes with a mineral acid.


Problem 36)

The following compounds (a-f) come from the ozone reaction of alkenes followed by treatment with a reductant such as Me2S.


Choose the appropriate alkene(s) from the following (I-VIII) for obtaining these compounds (a-f).

Problem 37)

Represent the products resulting from the treatment with OsO4 of the following alkenes (I-VI):


Problem 38)

Identify the conjugate systems of the following molecules (a-e), determining which would be suitable for the Diels-Alder reaction:


Problem 39)

Predict the product(s) (A-F) of the Diels-Alder reactions described below:


Problem 40)

Draw the structure of the 4 major products obtained in the radical polymerization of isoprene.


Problem 41)

Indicate the product(s) obtained when buta-1,3-diene is treated with:

  • a) 1 mol Br2
  • b) 1 mol HBr (-15 ºC)
  • c) 1 mol HBr (45 ºC)
  • d) propinoic acid
  • e) H2 / Pd(C)

Problem 42)

Complete the following scheme:


Problem 43)

Draw the structure of the hydrogenation products of 1,2-dimethylcyclohexene, (E)-but-2-ene and (Z)-but-2-ene.

Problem 44)

State the product(s) obtained on the addition of bromine in CCl4 to cyclohexene.

Problem 45)

The addition of chlorine in the presence of water on 1-methylcyclohexene gives rise to a pair of products which are enantiomers of each other. What would be their structures?

Problem 46)

Treatment of 3-ethyl-pent-2-ene with sulfuric acid in water leads to the formation of an alcohol. Deduce reasoned the structure of the product obtained.

Problem 47)

Describe the reactions and products obtained from cyclohexene and (E)-but-2-ene when they react independently with a) diazomethane and with b) peracetic acid.

Problem 48)

Justify the following result:


Problem 49)

Choose the appropriate dienes and dienophiles for obtaining the following adducts (a-j):


Problem 50)

Point out, in the following structures (a-c), which fragment acts as a diene and as a dienophile, and predict the carbon skeleton (disregarding stereochemistry) that would be obtained by an intramolecular Diels-Alder reaction.


Problem 51)

Justify the low reactivity of (Z,Z)-hexa-2,4-diene in the Diels-Alder reaction.