Tautomerism refers to an equilibrium between two different structure of the same compound. Usually the tautomers differ in the point of attachment of a hydrogen atom.

Tautomers are two forms of a compound that interconvert by a process known as tautomerization. A common type of tautomer is found with ketones. This is called keto-enol tautomerism. The ketone and its enol form are readily interconvertible constitutional isomers that exist in equilibrium with each other. Isomers that differ from each other only in the location of a hydrogen atom and a double bond are proton isomers. Proton tautomers are isomers in which a hydrogen atom and a double bond switch locations between a carbon atom and a heteroatom (which is an atom other than carbon, such as oxygen or nitrogen). There is a rule which states, called Erlenmeyer Rule, which states that all alcohols in which the hydroxyl group is attached directly to a double-bonded carbon atom become aldehydes or ketones. This occurs because the keto form is generally more stable than its enol tautomer. Tautomers differ from each other in locations of atoms as well as electrons, and so are NOT resonance contributors, which are different representations of the same structure.

See the Web Links to the left for some diagrams of molecules with are tautomers for a better understanding and more information.

The use of figures of speech in the language reveals the plasticity and adds beauty and meaning to the language. Given here is a figures of speech list, which are easy to learn.

Adjunction: Adjunction refers to a clause or a phrase, usually a verb, that is added at the beginning of a sentence. Here are a few examples of adjunction;

• Sings the bird as we walk on by.
• Good it is that fights the master with his dark lord,

Allegory: This figure of speech is an extended metaphor where the characters or actions in a literary work have a more imaginative meaning. The examples of allegory are;

• I feel like a dog today. I rolled out of my basket and munched on some biscuit-like cereal. Scratching as I got on the train, I sniffed a passing female. Aruooo!! Down boy! - Animal Farm, George Orwell
• By this I perceive thou art one of my subjects; for all that country is mine, and I am the Prince and God of it. How is it then that thou hast run away from thy King? - The Pilgrim's Progress, John Bunyan

Allusion: An allusion is an indirect or brief reference to a person, place or thing in a literary work. Examples of illusion -

• I doubt if Phaethon feared more - that time

  he dropped the sun-reins of his father's chariot

  and burned the streak of sky we see today -

  or if poor Icarus did - feeling his sides

  unfeathering as the wax began to melt,

  his father shouting: "Wrong, your course is wrong - Inferno, Dante

• This responsibility is too much for me. I feel as though I have an albatross around my neck. - The Rime of the Ancient Mariner, Samuel Taylor Coleridge

Alliteration: A repetition of particular consonant sound in the beginning of each word in close succession. Though alliteration is mainly consonant sounds, sometimes vowel sounds are also repeated. This figure of speech is mainly used in poetry. A few examples of alliteration:

• I have stood still and stopped the sound of feet. - Acquainted with the Night, Robert Frost
• Those tidal thoroughbreds that tango through the turquoise tide. - Dancing Dolphins, Paul McCann

Antithesis: An antithesis is a figure of speech where there is a juxtaposition of two contrasting ideas in a balanced clause or sentence. Some illustrations of antithesis:

• It was the best of times, it was the worst of times, it was the age of wisdom, it was the age of foolishness, it was the epoch of belief, it was the epoch of incredulity, it was the season of light, it was the season of darkness, it was the spring of hope, it was the winter of despair, we had everything before us, we had nothing before us, we were all going direct to Heaven, we were all going direct the other way. - A Tale of Two Cities, Charles Dickens
• If, as our dreaming Platonists report,

  There could be spirits of a middle sort,

  Too black for heav'n, and yet too white for hell,

  Who just dropp'd halfway down, nor lower fell. - The Hind and the Panther, John Dryden

Apostrophe: In this figure of speech, a non existent or absent person is addressed. In literary pieces, this figure of speech usually starts with an exclamation 'O'. Examples of apostrophe are:

• O Romeo, Romeo! wherefore art thou Romeo? - Romeo and Juliet, William Shakespeare
• O, pardon me, thou bleeding piece of earth, / That I am meek and gentle with these butchers! / Thou art the ruins of the noblest man / That ever lived in the tide of times. - Julius Caesar, William Shakespeare.

Climax: In climax, the words or clauses are arranged in ascending order of importance. These phrases have a similar theme and arranged in increasing order according to the impact they create on the reader. A few illustrations;

• Love creates happiness, happiness creates joy, joy creates enlightenment.
• We'll collect pennies in tens, hundreds and millions! Power starts small, becomes significant then becomes unstoppable.

Euphemism: A figure of speech where an offensive or rude word is substituted by a polite and gentle word. The technique is to use a neutral language so as not to sound offensive to the receiver. Like for instance:

• Differently abled instead of disabled.
• Put to sleep instead of euthanasia

Hyperbole: It is used while exaggerating something. This figure of speech is mainly used in several jokes or as a way of insult. It is to dramatize a normal situation or to make it look worse. Somehyperbole examples:

• The whole world was staring at me.
• It is going to take a zillion years to get through medical school.
• My backpack weighs a ton.

Irony: Irony is used to convey the opposite meaning of a word. It is usually used in sarcasm or in humor. It is also used to convey an ugly truth in a subtle manner. Some examples of irony are:

• "Water, water, everywhere,

  And all the boards did shrink;

  Water, water, everywhere,

  Nor any drop to drink." (Situational Irony) - The Rime of the Ancient Mariner, S. T. Coleridge

• The boy is so intelligent that he failed in all the subjects. (Verbal Irony)

Metaphor: Metaphor is used for the purpose of comparison with a thing which is not applicable to it literally. It is an indirect comparison of two unrelated things. Some examples of metaphors include:

• He was a lion in the battlefield.
• He is the apple of my eye.

Metonymy: In metonymy, the name of one thing is replaced with something that is closely related to it. In common terms, it is also known as misnomer or transmutation. Here are some metonymy examples:

• The suits on Wall Street walked off with most of our savings. (Suits referring to bankers).
• The White House asked the television networks for air time on Monday night. (Here air time refers to broadcasting).

Onomatopoeia: This figure of speech imitates the sounds produced by the objects or actions. Examples of onomatopoeia:

• The buzzing of bees.
• The whirring of the washing machine.

Oxymoron: Using a contradictory term to define a situation, object or event is oxymoron. Some oxymoron examples are:

• Clearly misunderstood
• Exact estimation

Personification: Associating an inanimate object to human quality. A few personification examples are:

• The haughty lion surveyed his realm
• My car was happy to be washed.

Simile: Simile is a figure of speech where two essentially unlike things are compared with each other, using 'as', 'than' or 'like'. Simile examples are:

• O my love is like a red, red rose.
• Life is like an onion: You peel it off one layer at a time, and sometimes you weep.

Synecdoche: It is a part of speech similar to metonymy, where a part of a particular object is used to refer to the whole thing. Synechdoche examples are:

• The city posted a sign, where 'the city' refers to the government.
• The gray beard refers to an old man.