Assignment on polyhydroxy alcohol by nasif123

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   Juthika Sarker
   Topi Rizan Alam
   Maisha Kabir
   Tasana Azad
   Al-Akaid Badhan

Submitted to: EASHA ROY
   Alcohols are compounds that have hydroxyl groups (-
    OH) bonded to saturated, sp3- hybridized carbon
    atoms. Alcohols are compounds of general formula
    ROH, where R is any alkyl or substituted alkyl group.

   Compounds which contain more than one –OH group
    are called polyhydric alcohols or polyols.

   They are further classified according to the number of –
    OH groups present in the molecule for example,
    dihydric alcohols, tridydric alcohols,etc.
(1)   1,2-Ethanediol   (2) 1,2,3-propanetriol
      CH2- CH2              CH2-CH2-CH2
      OH   OH               OH OH OH

 (3) 1,3-propanediol    (4) glycerol
      H HH                  H H H
 HO-C-C-C-OH             HO-C-C-C-OH
      H HH                  H HO H
  (1)Lower diols are colorless viscous liquid.
  (2) They are soluble in water.
(3) Their boiling points are much higher then those of
     monohydric alcohols of similar molecular weight.


R         O---------H          O

    * polyhydroxy alcohol provide more than one site per molecule for
      hydrogen bonding. The simplest diol, ethane-1,2-diol (ethylene glycol),
      boils at 97 °c.


Esters                                     Aldehydes

   Compounds which contain two –OH groups on
    different carbon are called dyhydric alcohols or diols.

   They are rarely found in nature as they are very
    unstable and undergoes spontaneous decomposition to
    give corresponding carbonyl compound.

   Diols are commonly known as glycols since they have
    sweet taste.
      It is prepared in the following ways:
(1)   By oxidation of ethylene with cold dilute potassium
      permanganate solution.
(2)   By hydrolysis of 1, 2-dibromoethane with aqueous
      sodium carbonate solution.
(3)   By hydrolysis of ethylene chlorohydrins with sodium
(4)   By hydrolysis of ethylene oxide with H2O at 200 °c
      under pressure with dilute H2SO4 at 60 °c.
(1) Ethylene glycol is colorless viscous liquid, bp- 197 c,
    mp- -13.
(2) It has a sweet taste

(3) It is hygroscopic

(4) It is miscible with water and ethanol in all proportions
    but is insoluble in ether. It is as toxic as methyl alcohol
    when taken orally.
   CH2 + (H20 + 0) COLD KMNO4             CH2-OH
   CH2                                  CH2-OH
* Preparation of diol from permanganate.
    Trimethylene glycol (Propane- 1,3-diols):
    B.P- 214 C.
    May b prepared by the hydrolysis of trimethylene dibromide.
    CH2- CH2- CH2                          CH2- CH2-CH2
    ⌡           ⌡                         ⌡         ⌡
    Br         Br                         OH         OH
    Tetra methylene glycol ( Butane- 1,4-diol) :
     B.P- 230 C
    Tetra methylene glycol is prepared industrially by hydrogenating
   Pentamethylene glycol (Pentane-1,5-diol):
    Br(CH2)(CH2)3 CH2Br   CH3CO2K   CH3COOCH2
                      HOCH2(CH2)3 CH2 OH ◄┘
   Completely substituted 1,2- diols, such as 2,3-
    dimethyl-2,3-butanediol, are called pinacols. on
    treatment with mineral acids (HCL) they undergo
    dehydration and rearrangement to form ketones. This
    reaction is called pinacol- pinaclone rearrangement.
    For example:
     CH3CH3                              CH3
CH3-C –C- CH3          H+        CH3- C-C-CH3
     OH OH                            O CH3
 2,3-dimethyl-2,3-butanediol    3,3-dimethyl-2butanone
    (pinacol)                        (pinaclone)
   Compounds which contain three –OH groups are
    called trihydric alcohols or triols.
   An increase in number of –OH groups enhances the
    hydrogen bonding ability and therefore causing an
    increase in B.p.
    Tetrahydric Alchohols:
    Exists in three forms-
    Dextrorotatory erythritol; m.p- 88 C
    Laevorotatory erythritol; m.p- 88 C
    Meso- erythritol; m.p- 121.5 C
    Pentaerythritol :
    Pentitols is prepared by the condensation of formoldehyde with
    Hexahydric Alchohols:
       HOCH2(CHOH)4 CH2OH.
  May be prepared by reducing the corresponding aldohexoses.
Example: D-sorbitol, D-mannitol, L-sorbitol, L-mannitol.
  Glycerol or1,2,3-propantriol in the most important
   trihydric alcohol. It is formerly known as glycerin.
 Glycerol is found in all natural fats and oils as glyceryl
   esters of long chain carboxylic acids
 It can be manufactured in the following ways:

(1)From fats and oils: natural oils and fats are triesters of
   glycerol and long chain carboxylic acids ( mainly
   palmitic , stearic and oleic acids). On hydrolysis with
   alkali, the fats and oils produce glycerol and the salts of
   long chain acids which are called soaps:
CH2 OOCR                   CH2OH
CH2OOCR      +3NaOH         CHOH       +3RCOONa
CH2OOCR                    CH2OH         (soap)
                    (1,2,3- propantriol)

(2)From propene: Today much of glycerol is
   manufactured from propene obtained by the catalytic
   cracking of petroleum
   Most lipids are triglycerides. These are made from the
    alcohol glycerol. Glycerol has three hydroxyl groups,
    all of which can condense with a fatty acid. Usually all
    three undergo condensation reactions and the lipid
    formed is therefore, called a triglyceride.
   Triglycerides are the common lipids in nature and are
    further classified as fats or oils.

                      Fatty acid

                      Fatty acid
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