Introduction:
Alcohols are the compounds in which hydrogen of an alkane has been substituted by an -OH group. They encompass -OH group (that is, a hydroxyl) bonded to a saturated alkane such as carbon atom R-OH where 'R' is any simple alkyl or substituted alkyl group. For illustration:
CH3OH CH3CH2OH
Methanol Ethanol
Classes of Alcohols:
Alcohols can have one or more hydroxyl group. It could be:
1) Monohydric: It contain only one hydroxyl group. For illustration: ethanol.
CH3-CH2-CH2-OH
Ethanol
2) Dihydric: It contains two hydroxyl groups. For illustration: ethane-1, 2-diol.
3) Trihydric: It contains three hydroxyl groups. For illustration: propane-1, 2, 3-triol.
Usually with more than one hydroxyl group, it is stated to be polyhydric.
Monohydric alcohols encompass the general formula CnH2n + 1OH. They can be categorized into three classes: primary (1o), secondary (2o) and tertiary alcohol (3o) according to the number of alkyl groups joined to the hydroxyl-bonded carbon atom.
a) Primary alcohol (1°):
It consists of one alkyl group attached to the hydroxyl bonded carbon atom.
Fig: Primary alcohol
For example: CH3OH CH3CH2OH
b) Secondary alcohol (2o):
There are mainly two alkyl groups joined to the hydroxyl-bonded carbon atom.
Fig: Secondary alcohol
c) Tertiary (3o):
There are mainly three alkyl groups; however no hydrogen atom directly attached to the hydroxyl-bonded carbon atom.
Fig: Tertiary alcohol
Naming Alcohols:
a) Common names:
Simple alcohols are often known by their common names that comprises of the name of the alkyl group to which the -OH group is attached followed by the term 'alcohol'.
For illustration:
Methyl alcohol Ethyl alcohol
b) IUPAC names:
In the IUPAC system, alcohols are termed as alkanols and their names are derived from the parent alkane via replacing the 'e' from the parent hydrocarbon and adding the suffix 'ol'.
CH3CH2OH CH3CH2CH2OH
Ethanol Propanol
c) Glycols:
Dialcohols or diols are known as glycols. They are named as the derivatives of parent hydrocarbon by the -diol name ending added. The -OH groups are added as the prefixes.
HOCH2CH2OH
1, 2-Ethanediol
Physical Properties of Alcohols:
1) Physical Appearance:
Most of the simple alcohols are liquid at room temperature. Alcohols having more than twelve carbon atoms are waxy solid at room temperature.
2) Melting and boiling point:
Similar to the parent hydrocarbon, the boiling points among the alcohols increase gradually by the increase in the number of carbon atoms. The boiling point of alcohols is extremely high as compared with that of the corresponding alkane as their capability to form hydrogen bond between the hydrogen atom of the hydroxyl group and the oxygen atom of the other molecule.
The influence of the -OH group though becomes less significant as the carbon skeleton rises.
The order of boiling points of the isomeric alcohols is as follows:
1° alcohol > 2° alcohols > 3° alcohols
3) Density:
The density of alcohols increases by increasing the relative molecular mass, though, branching can decrease this effect.
All the simple alcohols are less dense than water; however the aromatic homologues are slightly denser than water.
4) Solubility:
Hydrogen bonding in alcohols affects their solubility in water. Alcohols by a relatively short carbon skeleton are soluble in water. For illustration: methane, ethanol, propan-1-o1 and propan-2-o1 are fully miscible with water in all chains increases, the solubility of alcohols drop drastically.
All the alcohols are miscible by most organic solvents like hexane, benzene and ethanol; the smaller ones are helpful organic solvents.
Tutorsglobe: A way to secure high grade in your curriculum (Online Tutoring)
Expand your confidence, grow study skills and improve your grades.
Since 2009, Tutorsglobe has proactively helped millions of students to get better grades in school, college or university and score well in competitive tests with live, one-on-one online tutoring.
Using an advanced developed tutoring system providing little or no wait time, the students are connected on-demand with a tutor at www.tutorsglobe.com. Students work one-on-one, in real-time with a tutor, communicating and studying using a virtual whiteboard technology. Scientific and mathematical notation, symbols, geometric figures, graphing and freehand drawing can be rendered quickly and easily in the advanced whiteboard.
Free to know our price and packages for online Chemistry tutoring. Chat with us or submit request at info@tutorsglobe.com
tutorsglobe.com protozoan microbiology assignment help-homework help by online microbiology tutors
tutorsglobe.com american art assignment help-homework help by online humanities tutors
tutorsglobe.com site of photosynthesis assignment help-homework help by online photosynthesis tutors
www.tutorsglobe.com offers Data Objects Attributes and Relationships homework help, assignment help, case study, writing homework help, online tutoring assistance by computer science tutors.
tutorsglobe.com art criticism assignment help-homework help by online humanities tutors
tutorsglobe.com change of electron affinity along a group assignment help-homework help by online electron affinity tutors
tutorsglobe.com phospholipids assignment help-homework help by online lipid metabolism tutors
tutorsglobe.com extraction of silver assignment help-homework help by online occurrence and principles of extraction of silver tutors
Roles of Insects and Mites as Pests and Parasites tutorial all along with the key concepts of Parasitic Mites, Parasitic mites of mammals, birds and humans, Parasitic mites of invertebrates, Insect Pests, Parasitic Insects, Biting midges, Tsetse flies and Bed bugs
Classification of Cost according to functions - Production Costs, Administrative Costs, Selling and Distribution Costs, Research and Development Costs.
tutorsglobe.com protein model assignment help-homework help by online protein structure tutors
www.tutorsglobe.com offers alkyl halide occurrence homework help, alkyl halide occurrence assignment help, online tutoring assistance, organic chemistry solutions by online qualified tutor's help.
tutorsglobe.com importance of economic laws assignment help-homework help by online economic laws tutors
Theory and lecture notes of Prisoners Dilemma all along with the key concepts of prisoners dilemma, Cheating on the Cartel, dominant strategy. Tutorsglobe offers homework help, assignment help and tutor’s assistance on Prisoners Dilemma.
tutorsglobe.com ascomycotina assignment help-homework help by online division eumycota tutors
1956787
Questions Asked
3689
Tutors
1490912
Questions Answered
Start Excelling in your courses, Ask an Expert and get answers for your homework and assignments!!