ORGANIC CHEMISTRY

ORGANIC CHEMISTRY

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Organic Chemistry
Organic Chemistry study deals with the production of organic molecules and their reaction paths, interactions, and uses. Organic chemistry is a branch of chemistry that deals with the study of the structures, composition, and synthesis of carbon-containing compounds. For a good understanding of this type of chemistry, it is essential to make a note of the fact that that every organic molecule in addition to containing carbon also contains hydrogen. Although it is true that organic compounds can contain other elements, it is the bond between carbon and hydrogen that makes a compound organic.

 

Initially, Organic Chemistry was defined as the study of compounds formed by living organisms, but the definition was later widened to also encompass synthetically synthesized substances. Prior to the year 1828, every organic compound was obtained from living organisms.

Nomenclature of Alkanes
The table below illustrates the systematic names and arrangements of the first twenty straight chain alkanes. It is essential to get familiar with them as form the basis for naming countless other organic molecules all through your course of study.

Alkyl Groups
Alkanes can be depicted by the general formula CnH2n+2. An alkyl group is derived by removing one hydrogen from the alkane chain, and it can be depicted by the formula CnH2n+1. The removal of the one hydrogen gave rise to a stem change from -ane to –yl as exemplified in the examples below:

Similar concept can be applied to every straight chain alkane available in the table below:

Name Molecular Formula Condensed Structural Formula

Methane - CH4 - CH4

Ethane - C2H6 - CH3CH3

Propane - C3H8 - CH3CH2CH3

Butane - C4H10 - CH3(CH2)2CH3

Pentane - C5H12 - CH3(CH2)3CH3

Hexane - C6H14 - CH3(CH2)4CH3

Heptane - C7H16 - CH3(CH2)5CH3

Octane - C8H18 - CH3(CH2)6CH3

Nonane - C9H20 - CH3(CH2)7CH3

Decane - C10H22 - CH3(CH2)8CH3

Undecane - C11H24 - CH3(CH2)9CH3

Dodecane - C12H26 - CH3(CH2)10CH3

Tridecane - C13H28 - CH3(CH2)11CH3

Tetradecane - C14H30 - CH3(CH2)12CH3

Pentadecane - C15H32 - CH3(CH2)13CH3

Hexadecane - C16H34 - CH3(CH2)14CH3

Heptadecane - C17H36 - CH3(CH2)15CH3

Octadecane - C18H38 - CH3(CH2)16CH3

Nonadecane - C19H40 - CH3(CH2)17CH3

Eicosane - C20H42 - CH3(CH2)18CH3

Alkoxy Groups(Alkoxides)
Alkoxides are composed of an organic group bonded an oxygen atom that is negatively charged. Generally, they are written as RO-, where R stands for the organic substituent. Related to what obtainable in alkyl groups earlier discussed, the concept of naming alkoxides can be applied to every straight chain alkanes in the above table. and so on.

Three Basic Principles of Naming in organic chemistry

Select the longest, mainly substituted carbon chain containing a functional group.

A carbon that is bonded to a functional group must be the carbon atom in the chain with the lowest possible number. If there are no functional groups, next any substitute present should be given the smallest possible number.

After putting the 1st and second rules into consideration, ensure that you consider the alphabetical order and that your substitutes and/or functional groups are noted in alphabetical order.

Common Names of Branched Alkanes
A number of branched alkanes have common names that are still widely made use of today. These common names use prefixes like iso-, sec-, tert-, and neo-. The prefix iso-, stands for isomer. It is frequently given the name 2-methyl alkanes. What this means is that during naming, if there is methyl group situated on the second carbon of a carbon chain during naming, we could make use of the prefix iso-. The prefix will be placed in front of the alkane name which showcases the total number of carbons.

Examples are:

• Isopentane. This is the same as 2-methylbutane

• Isobutene This is the same as 2-methylpropane

To be able to allocate the prefixes sec-, which represents secondary, and tert-, which represents tertiary, it is essential that we first and foremost study how to classify carbon molecules. If a carbon is attached to only one other carbon, it is referred to as a primary carbon. If a carbon is attached to two other carbons, it is referred to a secondary carbon. A tertiary carbon is a carbon atom attached to three other carbons and finally, a quaternary carbon is a carbon that has carbon atom attached to it.

For instance:

• 4-sec-butylheptane (30g)

• 4-tert-butyl-5-isopropylhexane (30d);

Example of the usage of the prefix neo-

• neopentane

• neoheptane

Nomenclatures of Alkenes
Alkenes are a class of hydrocarbons that contain only carbon and hydrogen with a double bond. They are unsaturated compounds that contain at in the slightest one carbon-to-carbon double bond. Alkenes are also known as olefins.

Alkenes possesses carbon-carbon double bonds and are unsaturated hydrocarbons with the molecular formula is CnH2n. This is as well the same molecular formula that of cycloalkanes. Alkenes are named by leaving off the -ane ending of the parent alkane and replacing it with -ene.

Introduction of Alkene
The parent structure is the longest chain containing both carbon atoms of the double bond. The two carbon atoms of a double bond and the four atoms attached to them recline in a flat surface, with bond angles of approximately 120°. A double bond consists of one sigma bond created by overlap of sp2 hybrid orbitals and one pi bond fashioned by overlap of parallel 2 p orbitals.

The Basic Rules
For straight chain alkenes, it is equivalent basic rules as nomenclature of alkanes apart from the alteration with the suffix to "-ene."

i. Discover the Longest Carbon Chain that is bearing the Carbon to Carbon double bond. In a situation where we have two ties for longest Carbon chain, and both chains is bearing a Carbon to Carbon double bond, the most substituted chain should be discovered.

ii. The Carbon to Carbon double bond should be given the lowest possible number.

There is no need to number cycloalkenes due to the fact that the double bond is situated one position.

Alkene that possess equivalent molecular formula but which has the double bonds located in a different position is referred to as constitutional isomers.

The priority of Functional Groups during naming:

iii. After the two rules above, add substituents and their location to the alkene as prefixes. Do keep in mind to assign the lowest possible numbers. You must not forget to name them in alphabetical order when writing them.

iv. The next thing to do is to identify stereoisomers. When there are only two non hydrogen that are attached to the alkene, you should use cis and trans to name the molecule.

v. On the contrary when there there are 3 or 4 non-hydrogen dissimilar atoms attached to the alkene , you should use the E, Z system.

vi. Note that the hydroxyl group proceeds over the double bond. Consequently, alkenes possessing alcohol groups are referred to as alkenols. And the prefix for this group becomes -enol. And this means that in this group, the alcohol takes up the lowest priority against the alkene.

vii. Finally, note that alkene substituents are called alkenyl with the suffix -enyl.

Below is the systematic name and molecular formula of the first twenty straight chain alkenes.

Name - Molecular formula

Ethene - C2H4

Propene - C3H6

Butene - C4H8

Pentene - C5H10

Hexene - C6H12

Heptene - C7H14

Octene - C8H16

Nonene - C9H18

Decene - C10H20

Undecene - C11H22

Dodecene - C12H24

Tridecene - C13H26

Tetradecene - C14H28

Pentadecene - C15H30

Hexadecene - C16H32

Heptadecene - C17H34

Octadecene - C18H36

Nonadecene - C19H38

Eicosene - C20H40

Geometric Isomers
Double bonds can occur as geometric isomers and these isomers are selected by making use of the cis / trans designation or the modern E / Z designation.

cis Isomers
For Cis Isomers, the two largest groups are on the same side of the double bond.

trans Isomers
For trans Isomers, the two largest groups are on the opposite sides of the double bond.

Nomenclature of Alkynes
Alkynes are organic molecules that are made of the functional group of carbon-carbon triple bonds. Their empirical formula is CnH2n-2. They are unsaturated hydrocarbons. Similar to the alkenes they have the suffix –ene, alkynes use the ending –yne. This suffix is employed when there is only one alkyne in the molecule.

Below are the molecular formulas and names of the first ten carbon straight chain alkynes.

Name - Molecular Formula

Ethyne - C2H2

Propyne - C3H4

1-Butyne - C4H6

1-Pentyne - C5H8

1-Hexyne - C6H10

1-Heptyne - C7H12

1-Octyne - C8H14

1-Nonyne - C9H16

1-Decyne - C10H18

Ethyne is commonly known as acetylene. It is being made use of industrially.

Naming Alkynes
Just like the alkane and alkene the IUPAC rules are made use of while naming naming alkynes. Below are the rules to follow:

Rule no 1

Look for the longest carbon chain that contains the two carbon atoms of the triple bond.

Rule no 2

Assign number to the longest chain beginning from the end nearest to the triple bond. A 1-alkyne is known as a terminal alkyne and alkynes at any other place is referred to as internal alkynes.

For instance:

4-chloro-6-diiodo-7-methyl-2-nonyne

Rule 3

After assigning numbers to the longest chain with the lowest number, tag every one of the substituents at its equivalent carbon. In writing out the name of the molecule, organize the substituents in alphabetical order. If the substituents are more than one, they should be differentiated with the prefixes di, tri, and tetra for two, three, and four substituents correspondingly. These prefixes are not written in alphabetical order.

For instance:

1-triiodo-4-dimethyl-2-nonyne

Aromatic Hydrocarbons-Benzene

The adjective "aromatic" is employed by organic chemists in a relatively dissimilar way than what is usually applied.

Benzene

Properties/reactions of benzene

• Specific Substitution Reactions of Benzenes

• Electrophilic Aromatic Substitution of benzene

• Electrophilic Substitution of Disubstituted Benzene Rings

• Nucleophilic Reactions of Benzene Derivatives

• Reactions of merged Benzene Rings

• Reactions of Substituent Groups

• Substitution Reactions of Benzene Derivatives

Alchohols
Alcohols are among the most part significant molecules in organic chemistry. They can be prepared from a lot of dissimilar kinds of compounds and they can be transformed into various types of compounds. Alcohols are molecules possessing the hydroxy functional group (-OH) that is bonded to carbon atom of an alkyl or substituted alkyl. The hydroxy functional group powerfully adds to the physical properties of alcohols.

Nomenclature of Alcohols
In the IUPAC system of nomenclature, functional groups are usually nominated in one among two ways. The presence of the function may be showcased by a characteristic suffix and a location number. This is widespread for the carbon-carbon double and triple bonds which possess the respective suffixes ene and yne. Halogens, on the contrary do not possess a suffix and are named as substituents, for instance: (CH3)2C=CHCHClCH3 is 4-chloro-2-methyl-2-pentene.

Alcohols are normally named by the first procedure and are designated by an ol suffix, as in ethanol, CH3CH2OH

On longer chains, the position of the hydroxyl group decides the chain numbering. For instance

(CH3)2C=CHCH(OH)CH3 is 4-methyl-3-penten-2-ol.

For the mono-functional alcohols, this normal system is composed of naming the alkyl group followed by the word alcohol. Alcohols may as well be classified as primary, 1º, secondary, 2º & tertiary, 3º, in a similar manner to alkyl halides. This term is known as alkyl substitution of the carbon atom that is carrying the hydroxyl group. It is indicated with blue color in the diagram below.

Phenols
Compounds in which a hydroxyl group is bonded to an aromatic ring are known as phenols. The chemical behavior of phenols is dissimilar in some ways to that of alcohols. It is therefore sensible to discuss them as a similar but typically distinct group.