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THE PHOTO-MINIATURE

420

from coal-tar distillate. To the chemist it is known as Ce H,, which simply expresses the fact that the benzene molecule consists of six groups of atoms, each of these groups containing one atom of carbon (C) and one atom of hydrogen (H). In 1866, Kekule published the fact ltekule's that benzene behaves in its reactions Be:ua;on with other bodies as though the carbon atoins were linked together round the points or angles of a hexagon, each with a hydrogen atom attached to it. This gives us the famous Kekule hexagon formula for benzene, sometimes called the benzene ring. For clearness in what follows, we will show this graphically: (1) In full; (2) as generally abbreviated in use, the C and H atoins being supposed to be at each angle, except where the substitution of other atoms or groups is shown by the introduction of a new symbol; and (3) with the points numbered to show in which position any addition or substitution is made, this being of importance, as we shall see later. CD

1

HC ( ) CD

('/'

DC' CD CD (1)

6 5

('j

2 3

4 (2)

(3)

Thus far the simple but fascinating

Derivatives: benzene molecule. Now let us see how Phenol:

Aniline

the derivatives or substitution products are obtained. The hydrogen (H) atoins in benzene are easily replaceable by other atoms or chemical groups as, for instance, chlorine (Cl), hydroxyl (OH), or amido (NHz) groups. Thus we get:

n n n路 -Cl

'/

Chlor-bell.leoe

-OD

'-/ Hydroll)'-beoaeoe or Phrool (Carbolic Acid) (5)

'-/

Amido-be11.1eoe or Aniline (6)

Modern Photographic Developers  

A Practical Handbook to the New Developers Telling What They Are and How to Use Them with Reliable Formulae by The Photo Miniature, January...

Modern Photographic Developers  

A Practical Handbook to the New Developers Telling What They Are and How to Use Them with Reliable Formulae by The Photo Miniature, January...

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