source: testing lab


source: This

 formaldehyde : Chemical properties-

1) Condensation with phenol:

HCHO condenses with phenol to give a synthetic plastic bakelite. This reaction takes place in presence of dilute NaOH. Bakelite is used for preparing electrical insulators, electric switches, toys etc.


2) Condensation with urea :

HCHO also condenses with urea in acidic solution to form a plastic like product (formaldehyde urea plastic). It is used in the preparation of cup, plate, tray and glass etc.


3) Reaction with  alcohol:

HCHO reacts with CH3OH in presence of dry HCl, then methylal (dimethoxy methane) is formed.


4) Addition reactions of Formaldehyde :

a) Addition of H2—-

i) Aldehydes are reduced to primary alcohol.Reduction is carried out with LiAlH4/ether, H2/Pd,H2/Ni etc.

>C=O +H2 —->   >CHOH

HCHO + H2——> CH3OH (primary alcohol)

ii) Clemenson’s reduction-  When aldehydes are reduced with Zn-Hg/HCl then alkanes are formed.In this reaction >C=O is reduced to >CH2 group.

>C=O +4[H] —->   >CH2 +H2O

HCHO +4[H]——–> CH4  + H2O

b) Addition of HCN — Aldehydes on addition with  [NaCN & H2SO4] or HCN give cyanohydrins.

>C=O +HCN—–>    >C(OH) CN

HCHO + HCN—–>    HCH(OH) CN [formaldehyde cyanohydrin]

c) Addition of NaHSO3— form crystalline Sodium bisulphite  compound.

>C=O + NaHSO3 —–>    >C(OH) SO3Na

HCHO + NaHSO3—-> HCH(OH) SO3Na [formaldehyde sodium bisulphite compd]

d) Addition of Grignard reagent– Form addition product  which on hydrolysis give primary alcohol.

>C=O +RMgX —–>   >C(OMgX) R——–>   >C(OH) R [sec.alcohol]

HCHO + CH3MgBr —–>   HCH (OMgBr) CH3——–>    CH3CH2OH [primary alcohol]

5) Substitution reaction of Formaldehyde-

a) Reaction with Hydroxylamine – Oximes are formed.

>C=O + H2NOH——->       >C=NOH [oxime] +H2O

HCH=O + H2NOH——->       HCH=NOH [Formaldoxime]+H2O

b) Reaction with Hydrazene –  Hydrazones are formed.

>C=O + H2NNH2——->       >C=NNH2 [Hydrazone] +H2O

HCH=O + H2NNH2——->       HCH=NNH2[ formaldehyde hydrazone] +H2O

c)  Reaction with Phenyl Hydrazene –  Phenyl Hydrazones are formed.

>C=O + H2NNHC6H5 ——->       >C=NNHC6H5 [  Phenyl Hydrazone] +H2O

HCH=O + H2NNHC6H5——->  HCH=NNHC6H5 [Formaldehyde Phenyl  hydrazone] +H2O

d)  Reaction with Semicarbazide –  Semicarbazones are formed.

>C=O + H2NNHCONH2——->       >C=NNHCONH2 [  Semicarbazone] +H2O

HCH=O + H2NNHCONH2  —–>  HCH=NNHCONH2 [Formaldehyde Semicarbazone] +H2O

e) Reaction with Phosphorous pentachloride—  Methylene dichloride is formed.

>C=O + PCl5  ——>   >CCl2 +POCl3

HCH=O + PCl5  ——>   CH2Cl2 [Methylene dichloride] +POCl3


source: slide