Resins

The term resin‘ is applied to more or less solid, amorphous products of complex chemical nature. 

These mixtures of essential are oils, amorphous oxygenated products of terpenes and carboxylic acids. 

Resins and related resinous products are produced in plants during normal growth or secreted as a result of injury to the plants They are usually occur in schizogenous or schizolysigenous cavities or ducts.

General properties

Physical characters –

All resins are heavier than water , they are usually amorphous ,hard, and brittle solids.   

They are insoluble in insoluble in petroleum water ether and usually but dissolve more  or  less completely in alcohol, chloroform and ether. 

CHEMICAL PROPERTIES:

On heating, they soften and finally melt

Insoluble  in  water  and  usually  insoluble  in  petroleum  spirit,  but  dissolve  more  or  less completely in alcohol, chloroform and ether.

Chemically, resins are complex mixtures of resin acids, resin alcohols, resin phenols, esters and chemically inert compounds known as resenes. 

CLASSIFICATION:

Resin acid: carboxylic acid group containing resinous substances e.g. abietic acid & commiphoric acid 

Ester resins –  This group contains esters as chief the constituents of the resins- Examples Benzoin and Storax, Benzoin contains benzyl benzoate,  Storax contains cinnamyl cinnamate

Resin alcohols –    They occurs as in free state or as esters , examples – Balsam of peru with perru resino tannol Guaiaccum resin with guaic resinol

Resin phenol (resino tannols): contains phenol group e.g. peru- resinotannol in peru balsam & tolu-resinotannol in tolu balsam & siaresinotannol in benzoin

Gluco resins: resins when get combined with sugars by glycosylation e.g. Convolvulaceae family drugs.

Resin: stable, neutral, unaffected by most chemical reagents or by exposure to moisture produced a hard film. e.g. asafetida

Oleo resin: resin+ volatile oil e.g. turpentine, ginger, copaiba, Canada

Gum resin: resin+ gum e.g. ammoniacum

Oleogum resin: resin+volatile oil+gum e.g. myrrh, asafetida, gamboges

Balsam: contains aromatic acids like benzoin & cinnamic e.g. Tolu balsam, peru balsam, storax

CHEMICAL COMPOSTION 

Complex mixture of acids, alcohols, phenols, esters, glycosides or hydrocarbons.

When  associated  with  volatile  oils,  contains  monoterpenoids,  sesequiterpenoid  and diterpenoids. 

Gums when associated with resin: acacia gum: oxidase enzymes.

ISOLATION:

Difficult task due to presence of various combinations.

Extraction  with  alcoholic  solvents  and  then  the  subsequent  precipitation  by  adding concentrated alcoholic extract to a large proportion of water. 

Hydro distillation or distillation can be used for separation of volatile oils from resins. (separation of resin from turpentine)

Uses

Plant resins

Plant resins are valued for the production of varnishes, adhesives, and food glazing agents. 

They are also prized as raw materials for the synthesis of other organic compounds and provide constituents of incense and perfume. 

The oldest known use of plant resin comes from the human babies in late Middle Stone Age in Southern Africa where it was used as an adhesive for hafting stone tools. 

The hard transparent resins, such as the copals, dammars, mastic, and sandarac, are principally used for varnishes and adhesives, 

while the softer odoriferous oleo-resins, and gum resins containing essential oils are more used for therapeutic purposes, food and incense. 

The resin of the Aleppo Pine is used to flavour retsina, a Greek resinated wine.

Synthetic resins

Many materials are produced via the conversion of synthetic resins to solids.

Important examples are bisphenol A diglycidyl ether, which is a resin converted to epoxy glue upon the addition of a hardener. 

Silicones are often prepared from silicone resins via room temperature vulcanization.