Introduction: room temperature. Are toxic and solubleIntroduction: room temperature. Are toxic and soluble

                

Introduction:

Organosilicon
compounds are the organometallic compounds having at least one direct C-Si
bond. They are described as any series of derivative of silicon that have at
least one alkyl or aryl group especially one containing C-Si bond. Examples
include

We Will Write a Custom Essay Specifically
For You For Only $13.90/page!


order now

Tetramethylsilane,
tetraethylsilane, trimethylvinylsilane, silanol, siloxides, silene,
trimethylallylsilaneetc..

Historical introduction:

In
1863, two scientist Friedal and Crafts frist synthesized the organosilicon
compound Tetraethylsilane.

TETRAETHYLSILANE:

It
is made in high yield  from silicon
tetrachloride and various organometal derivatives, notably ethylmagnesium halides
or ethyl-lithium. The first preparation of organosilicon compound in 1863
involved the use of diethylzinc.

 

Apart
from difficult nucleophilic and electrophilic cleavage of the Si-C bond
reffered to earlier ,tetraethylsilane decomposes on strong heating to give
ethane and Si-H bond; this dehydrosilation method is  markedly catalyzed by metal oxides, and is
general for all alkyls other than methyl

Later,
in 1945 there had been direct synthesis of the chlorosilanes in the presence of
a catalyst establishing the modern organicsilicon industry. All of this has
created the conditions for the production of organic silicon with the
functional group. It is similar to most of organic compounds but also differ.
For example: The silicone -Si only contain single bond between the silicon
atoms . Simple types contain halosilcanes. For example:CH3SiCl (
trimethylchlorosilane) , silanol  (CH3SiOH)
, silyl ethers (CH3)3Si-O-Si(CH3)3 and
so on.

Properties:Such
compounds have special properties such as they are being able to polymerized in
to poly- siloxanes (silicones) ,are resistant to heat and water and have
electrical insulation properties and are being able to use for manufacturing of
silicone oil, silicone rubber and silicone resin.

They
are colourless or transparent liquids at room temperature. Are toxic and  soluble in many organic solvents. Are
corrosive and  prone to burn, produce
toxic fumes in the case of oxidants, fire and heat. Phenylsilane in contact
with steam produce toxic gasses. It is used as the water repellent, silicide
intermediates in industry and use in the synthesis of polymer organic silicide .in
the management of dangerous silicide as flammable liquids. Phenyl it is also
classified as the corrosive substance.

SILICON/SILICONE/ORGANOSILICON

SILICON
is naturally occurring chemical element and is 14th element in the
periodic table. It is a metalloid meaning it has the properties of both metal
and non-metal. It is second most abundant element in the earth crust after
oxygen. It readilys bounds with the oxygen and rarely found in nature in its
pure form. It is mosthy found in the form of silicon dioxide ( SiO2
) and silica better known as quartz which is most common component of sand.
Silicon and oxygen  mix with reactive
metals, the result is the class of minerals called silicates which include granite, feldspar, mica. A silicate is  the compound containing an anionic silicon
compound , hexafluorosilicate      SiF6 2- type of
silicates also exist.

 

SILICATE  ANION                  

SILICONE
is a synthetic substance it is a synthetic polymer made up of silicon , oxygen
and other elements such as carbon and hydrogen. It is generally a liquid or
flexible rubber like plastic and has useful properties such as low toxicity and
high heat resistance. And also provides good electrical insulation. Silicones
are also known as the polysiloxanes
can be defined as polymers that include inert, synthetic compounds made up of
repeating units of ”siloxanes” which is a chain of alternating silicon atoms
and oxygen atoms frequently combined with carbon/hydrogen.

It
consist of inorganic silicon-oxygen backbone chain -Si-O-Si-O-Si-  with organic side groups attach to silicon
atoms. These silicon atoms are tetravalent , so silicones ar.e polymers constructed
from  monomers and have general chemical
formula (R2SiO)n

We
can think silicon atom as having ”four hooks” that can link to other atoms
and oxygen atoms as having ‘two hooks” with all the links serves as the base
for integrated circuits (microchips).

ORGANO-SILICON
compounds are organometallic compounds containing direct C-Si bonds. It
describes any series of derivative of silicon that have at least one alkyl or
aryl group , especially one containing atleast on C-Si bond. They act as a
monomer in the formation of the silicones. SILICONES are the polymers of the
organo-silicon .

 

       organosilicon 

Silicone
polymer

PREPARATION:

The  organosilicon compounds are derived by the
direct reaction of alkyl chlorides with the silicon copper alloy while the main
and sought-after product is dimethyldichlorosilane.

2CH3-Cl+ Si(Cu)?(CH3)2SiCl2

The
organosilicon compounds are also prepared in laboratory by many methods some of
which are given below

They
can be prepared by the reaction of silicon tetrachloride with organo-lithium

They
can be prepared by the reaction of trialkylsilylchloride with Grignard reagent

By
reduction reaction of dialkyldichlorosilane with lithium aluminium hydride

Also
can be prepared by reaction of trichlorosilane with unsaturated compound such
as alkene etc…

BY HYDROSILYLATION METHOD:

After
direct process the second major method for the formation of Si-C bond is
hydrosilylation   (hydrosilation ) . in
this process the hydrosilanes adds to the unsaturated substrates , mostly  alkenes are used ,  Alkynes , imines , ketones , aldehydes , etc..
can also be used

An
example is the hydrosilation of phenylacetylene

Hydrosilylation
requires metal catalyst especially those based on the platinum group metals.

REACTIONS:

Organosilicon
compounds involve reactions which involve the cleavage of C-Si bond by nucleophilic
or electrophilic substitution reactions. The order of ease of C-Si bond fission
is as

Si-C(aryl)?Si-C(aryl)?Si-C(alkyl)?Si-C(alkyl)

        ?             ?                     ?              ?

         E+         Nu-                  E+           Nu-

        (1)          (2)                   (3)           (4)

Type 1

The
reactions involve in the type 1 of organosilicon reactions is as

The
rate of   R3SiH-H exchange is
104 more as compared to the H-H exchange.

Type 2

This
reaction is called as the Sakurai
reaction and is   example of type 2
reactions

Type 3

This
type of reaction takes place in the presence of a strong Lewis acid catalyst
and also slow fission takes place in the presence of cc-acid

Type 4

This
type of reactions occur only in the presence of a strong nucleophile

The
C-Si fission can occur more readily if

1)      Ring
strain releases

2)      Good
leaving group is present in beta position

RELEASE OF RING STRAIN:

 

GOOD LEAVING GROUP IN
BETA-POSITION:

UNSATURATED
ORGANO-SILICON COMPOUNDS:

Unsaturated
organosilicon compounds are more reactive than saturated organo-silicon
compounds because

1)      Addition
reactions are possible at carbon to carbon double bond and triple bond.

2)      They
are useful intermediates in the synthetic chemistry.

3)      Si-C
bond can be readily cleaved

4)      Both
allyl and vinyl silanesareindespensible 
nucleophiles in the organic synthesis and can be used in the host
transformation.

EXAMPLE:

Tetramethylvinylsilane:

The
structure of this compound is given as

PREPRATION:

It
is prepared as follows

 

  Trimethylvinylsilane is thermally stable.
Si-Vinyl bond is generally resistant to cleavage by acids or alkalies. The
above reaction occurs at 200 degree celcius.         

Hydroboration
and epoxidation are possible without Si-C cleavage

 

ORGANOSILICON COMPOUNDS CONTAINING
OXYGEN

SILANOLS:

These
compounds are the analogues of the alcohols and are mostly prepared as follows

BY
HYDROLYSIS OF SILYL CHLORIDE

 

BY
OXIDATION OF SILYL HYDRIDES

SILOXIDES:

These
are deprotonated derivatives of silanols

 

 

SILOXANES:

Silanols
tends to dehydrate to give siloxanes

SILYL ETHERS:

They
have connectivity Si-O-C, they are typically prepared by the reaction of
alcohol with silyl chlorides

Used
in protection in organic synthesis.

Some other organosilicon compounds

SILENES:

Silences
are
the compounds containing C=Si bond. The first evidence of silene was given by
Guselnikov and Flowers in 1967 from the pyrolysis of dimethylsilacyclobutane.

SILOLE:

Siloles
are silacyclopentadienes, are members of large class of compounds called
metalloles. They are silicon analogues of cyclopentadienes and are regarded
efficient in electron transport.

 

                                        

Saturated organosilicon compounds:

They
have been much studied in last 20 years or so. They are generally prepared by
reaction of dihalides with di-grignard reagents or di-lithium
organo-derivatives. These may also be performed or prepared in situ. Coupling
with alkali metal is also possible

Example:

It
is also possible to couple chlorosilanes and alkenes with lithium

Cyclic unsaturated organosilicon
compounds:

These
can be preparedby coupling reactions between alkali metals, alkynes, and diorganochlorosilanes,
also by dehydrogenation of appropriately substituted silacycloalkanes. Direct
dehydrogenation of saturated cyclic organosilanes normally gives poor yield

Example:

Silacyclobutanes:

They
can be made by ring closure of dibromo compounds, using reactive metals or by
mild dehydrogenation of halogen-substituted silacyclobutanes

They
are highly susceptible to cleavage by electrophilic reagents eg; HCLO4_MeOH,
Br or by nucleophilic reagents eg: RLi, ROH.

 

 APPLICATIONS
OF ORGANOSILICON COMPOUNDS

Organosilicon
compounds have many applications some of which are as

1)      Organosilicon
compounds can be directly applied in the monomeric form eg: it can be made to
silicone polymer by hydrolysis and polymerization.

2)      They
can be used as anti-adhesive materials.

3)      They
can be applied to drug boosting hair growth and in anti-cancer drugs.

4)      In
the field of organic synthesis, it is used as reducing as well as protective
agent of the active groups.

Eg:

Trimethylsilylchloride
is used for the protection of the carbonyl groups as well can be used for the
protection of alcoholic groups

                            

5)      As
a kind of monomer it can be used as silylating agent as well as being used for
covering the surface of material.

6)      Can
also be used for the moisture protection of electrical insulating materials.

 

 

 

 

 

 

 

 

 

References:

1)    Applications
of organosilicon compounds.http://www.dowcorning.com(accessed
Dec 19,2017).

2)      Organosilicon
compounds introduction and applications. https://www.chemicalbook.com
(accessed Dec19,2017).

3)      Difference
of silicon and silicones.http://archive.boston.com/
(accessed Dec 19,2017).

4)      Silicone
and organosilicon.https://www.livescience.com(accessed
Dec 20,2017).

5)      Organometallic
chemistry.http://onlinelibrary.wiley.com(accessed
Dec 20,2017).

6)      Organosilicon
compounds. https://www.chemicalbook.com(accessed
Dec 20,2017).