Answer to Question #186345 in Organic Chemistry for Sam

Question

reaction mechanism types:

• Addition e.g. aldehyde or ketone with HCN

• Substitution e.g. halogenoalkane with aqueous NaOH

• Elimination e.g. halogenoalkane with ethanolic NaOH

• Addition-elimination e.g. aldehyde or ketone with 2,4-dinitrophenylhydrazine

explore and interpret the similarities and differences between each of the four mechanisms

Answer 1

[1]..Addition reactions are typical of unsaturated organic compounds—i.e., alkenes, which contain a carbon-to-carbon double bond, and alkynes, which have a carbon-to-carbon triple bond—and aldehydes and ketones, which have a carbon-to-oxygen double bond. An addition reaction may be visualized as a process by which the double or triple bonds are fully or partially broken in order to accommodate additional atoms or groups of atoms in the molecule. Addition reactions to alkenes and alkynes are sometimes called saturation reactions because the reaction causes the carbon atoms to become saturated with the maximum number of attached groups.

A typical addition reaction may be illustrated by the hydrochlorination of propene (an alkene), for which the equation is

CH₃CH = CH₂ + HCl → CH₃C⁺HCH₃ + Cl⁻ → CH₃CHClCH₃

[2].. Substition Reactions::These type of reactions are said to possess primary importance in the field of organic chemistry. For example, when CH₃Cl is reacted with the hydroxyl ion (OH-), it will lead to the formation of the original molecule called methanol with that hydroxyl ion. The following reaction is as shown below-

CH₃Cl + (−OH) ————-CH₃OH( methanol) + Cl-

One more example would be the reaction of Ethanol with the hydrogen iodide which forms iodoethane along with water. The reaction is as shown-

CH₃CH₂OH + HI———— CH₃CH₂OI + H₂O

Substitution Reaction Conditions

In order to substitution reaction to occur there are certain conditions that have to be used. They are-

• Maintaining low temperatures such as room temperature
• The strong base such as NaOH has to be in dilute form. Suppose if the base is of a higher concentration, there are chances of dehydrohalogenation taking place
• The solution needs to be in an aqueous state such as water

[3]..Elimination Reactions::An elimination reaction is a type of organic reaction in which two substituents are removed from a molecule in either a one- or two-step mechanism. ...

• In most organic elimination reactions, at least one hydron (H⁺) is lost to form the double bond: the unsaturation of the molecule increases.

From above data we can easily understand the differences and similarities between the various mention reactions.