Organic Chemistry - Some Basic Principles And Techniques - Class 11 Engineering Chemistry - Extra Questions

$$2$$ moles of $$HI$$ are consumed in the reaction.Ether bond between two phenol rings is not cleaved as it not give stable carbocation.

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The reaction mechanism is $$SN^1$$ and $$C^+$$ is formed where it is most stable [$$C^+$$ is carbocation].

$$NaBH_4$$ can reduce aldehydes,ketones to alcohols but generally do not reduce esters,carboxylic acids or amides.

Next homologue is differ by $$-CH_2$$ unit.

The next homologues of the given compound are:

The next homologue of $$ C_{3}H_{7}OH $$ is called butanol ($$ C_{4}H_{9}OH $$).

$$ CH_{4}O $$ and $$ C_{2}H_{6}O $$ belong to the same homologous series that has a general formula $$C_nH_{2n+2}O$$.

A succeeding members of a homologous series differ by $$CH_2$$ unit

$$CH_3-CH_3$$- Ethane

The molecular formula of the first member of a certain group of organic compound is $$CH_{2}O$$. The name and the molecular formula of the third member of this group is propanol and its molecular formula is $$C_{3}H_{6}O$$. The members of this group are in homologous series. The general name for this group is called aldehydes.

Ring is more Activated towards electrophilic substitution reaction due to the presence of $$-NHCOR$$ group which $$-I$$ and $$+M$$ effect.

$$\text{Name}$$	$$\text{Molecular formula}$$	$$\text{Condensed structural formula }$$	$$\text{Number of carbon atoms }$$	$$Number \ of -CH_{2}-units$$
Methane	$$CH_{4}$$	$$CH_{4}$$	1	1
Ethane	$$C_{2}H_{6}$$	$$CH_{3}-CH_{3}$$	2	2
Propane	$$C_{3}H_{8}$$	$$CH_{3}-CH_{2}-CH_{3}$$	3	3
Butane	$$C_{4}H_{10}$$	$$CH_{3}-CH_{2}-CH_{2}-CH_{3}$$	4	4
Pentane	$$C_{5}H_{12}$$	$$CH_{3}-CH_{2}-CH_{2}-CH_{2}-CH_{3}$$	5	5
Hexane	$$C_{6}H_{14}$$	$$CH_{3}-CH_{2}-CH_{2}-CH_{2}-CH_{2}-CH_{3}$$	6	6

2nd member means $$n=2$$

A homologous series may be defined as a group of a class of compounds, each member of which differs from the preceding or succeeding member by one $$CH_2$$. The members of the series are known as homologs.
Ethanal $$(CH_3CHO)$$ and propanal $$(CH_3CH_2CHO)$$ are two consecutive members of the homologous series of aldehydes. In these compounds, the physical properties such as melting point, boiling point, density, etc., gradually increase with the increase in the molecular weight.
The chemical properties of these compounds closely resemble due to the presence of the same functional group (aldehyde group) in them.

Methane ($$CH_4$$) is the simplest hydrocarbon. It is the first member of the alkane family. The general formula of the alkane family is $$C_nH_{2n+2}$$.

(i) $$CH_3-CH_2-CH_2-X$$

• The boiling point of the hydrocarbons increases with the increasing molecular mass.
• As molecular mass increases the intermolecular force of attractions (Van der Waal's force and London force) increases that require a higher amount of energy to break the bond.
• Therefore, the correct order is $$C_3H_6$$<$$C_4H_8$$<$$C_5H_{10}$$

(i) When green copper carbonate {$${ CuCO }_{ 3 }$$} is heated it decomposes forming copper oxide {$$CuO$$} and carbon dioxide {$${ CO }_{ 2 }$$}.

a homologous series is a series of compounds with the same functional group and similar chemical properties in which each successive member differs by $${ CH }_{ 2 }$$.Compounds within a homologous series typically have a fixed set of functional groups that gives them similar chemical and physical properties.  The name "homologous series" is also often used for any collection of compounds that have similar structures or include the same functional group, such as the general alkanes (straight and branched), the alkenes (olefins), the carbohydrates, etc. 

1st $${ CHBr }_{ 3 }$$ reacts with base $${ t }_{ Bn }OK$$ to $$:{ CBr }_{ 2 }$$ carbene. Now this : $${ CBr }_{ 2 }$$ inserts into one of the double bond of cyclopentadiene to form $$B$$ which contains a three membered rings. Now breaking of three membered rings and simultaneous leaving of $${ Br }^{ \left( - \right)  }$$ gives $$C$$. Subsequently $$C$$ gives an aromatic compound $$D$$ which is bromo benzene.

Both $$-NO_2$$ and $$-Cl$$ is deactivating. But $$-Cl$$ has ortho-para-directing effect. So, it dominates the ortho-effect over $$-NO_2$$ meta effect.

Conversion of $$B$$ to $$C$$ is called Sand-Meyer reaction.

This reaction is known as nucleophilic by molecular substitution reaction $$(S_N2)$$ 

The mechanism of reaction is $$SN^2$$ due to the presence of strong solvent $$Et_2O$$.

The mechanism of the reaction is $$SN^2$$ due to the presence of strong solvent $$Et_2O$$.

$$N:-2\rightarrow +2$$

In presence of $$Cl_{2}/FeCl_{3}$$, halogenation on benzene takes place on or the position to $$Cl$$, as $$Cl$$ is o, p-directing group for electrophilic substitution.

In the first step, Michael addition or 1, 4-addition takes place at alkene not on carbonyl as the base is not that strong to attack the carbonyl.

Molecular formula is $$C_{10}H_{18}$$

Reaction intermediate is formed from reactants in a chemical reaction, and react further to produce the final product.

A homologous series is a series of compounds with similar chemical properties and the same functional group differing from the successive members by $$-CH_2$$. Members of a homologous series can be represented by the same general formula.

A carboxylic acid has the formula RCOOH where R can be hydrogen or a hydrocarbon group such as an alkyl group. The hydrocarbon group could equally well be based on a benzene ring.

The sodium salt of a carboxylic acid will have the formula RCOONa.

In decarboxylation, the -COOH or -COONa group is removed and replaced with a hydrogen atom.

2 CO2 will release in the above reaction

The general formula for the homologues series of functional group -Cl is $$C_{n}H_{2n+1}Cl$$.

General Formula	$$C_n H_{2n}$$	$$C_n H_{2n-2}$$	$$C_n H_{2n+2}$$
IUPAC name of the homologous series	Alkenes	Alkynes	Alkanes
Characteristic bond type	Double bond	Triple bond	Single bond
IUPAC name of the first member of the series	Ethene	Ethyne	Methane
Type of reaction with chlorine	Addition	Addition	Substitution

The difference is of $$1$$ carbon and two hydrogen atoms i.e., – $$CH_2$$, and the mass difference is $$14$$ a.m.u.

$$-CH_2= 12+2 = 14$$
The difference between the mass of two successive members of the homologous series is $$14$$ which means the $$CH_2$$ group increases in the homologous series of hydrocarbons.

Homologous series: When the members of a hydrocarbon family obey the same general formula they are said to be in homologous series. The members in the series are arranged in increasing order of their molecular masses:
Example:
Alkane – $$C_nH_{2n+2}$$
$$CH_4$$ – Methane
$$C_2H_6$$ – Ethane
$$C_3H_8$$ – Propane
$$C_4H_{10}$$ – Butane
Properties:

1. The difference between two consecutive members of the homologous series is – $$CH_2$$ and mass $$14$$ a.m.u.
2.  They all show the same chemical properties and slight gradation in their physical properties.

The name of the second member of homologous series is Ethene with chemical formula $$C_2H_4$$ it belongs to the group of alkenes.

(A) The given reaction involves two steps. The first step is the nucleophilic addition and the second step is the dehydration.
The hydroxide ion abstracts acidic proton to form carbonation. The carbanion attacks another carbonyl group (this is an intramolecular nucleophilic attack). This is followed by protonation of oxygen and dehydration to form the product.
(B) The given reaction is a nucleophilic substitution reaction in which chloride ion is substituted with a methyl group. The product is obtained by the rearrangement of the epoxide ring. The methyl group of the Grignard reagent attacks the terminal carbon atom of the epoxide ring to form oxide anion. The oxide anion then attacks the carbon-bearing chlorine atom.
(C) The given reaction involves two steps. The first step is the nucleophilic addition and the second step is the dehydration. The aldehyde oxygen atom is protonated. This is followed by the nucleophilic attack of the amine nitrogen on carbonyl carbon. The $$-OH$$ group is then protonated and $$H_3O^+$$ is lost.
(D) The given reaction involves electrophilic aromatic substitution and involves dehydration (loss of a molecule of water). It also involves the formation of a carbocation intermediate.
The $$-OH$$ group is protonated. This is followed by electrophilic aromatic substitution.

The product formed is cyclohexene.

An equivalent of alcohol is protonated to its conjugate acid. Another equivalent of the alcohol then perform nucleophilic attack at carbon ($$S_N2$$), leading to displacement of  water $$OH_2$$ and formation of a new $$C-O$$ bond results in formation of $$ethoxy ethane$$. 

This is done in 4 steps:

It is an electrophilic substitution reaction. It follows $$SN^1$$ mechanism and the final products obtained are $$HCl$$ and the above element.

Since $$OTS^-$$ is better leaving group, it proceeds via $$S_N2$$ reaction resulting in inverted product.

Reduction of keto leads to aromatization of ring takes place.

Thus, $$NaBH_4$$ reduces carboxyl group to the alcohol.

Here $$A$$ in presence of $${ HClO }_{ 4 }$$ will form $$B$$ easily, because $$A$$ is not aromatic but $$B$$ is aromatic due to presence of $$\left( 4n+2 \right) \Pi $$ electrons in $$B$$ $$(n=0)$$. So aromaticity will be driving force for formation of $$B$$.

The $$NaBH_4$$ or Sodium Borohydride is a mild reducing agent thus it does not reduce carboxylic acid group, thus it will only reduce the ketonic group to corresponding alcohol.

(a) A homologous series is a group of organic compounds having similar structures and similar chemical properties in which the successive compounds differ by $$CH_{2}$$ group.

Cleavation of 2,2-dimethyl oxirane can be illustrated by above mechanism.

The melting and boiling point of the successive members of the homologous series of alcohols increase with the increase in molecular mass.