Organozinc compounds can be prepared by heating zinc fillings with an alkyl halide in a carbon dioxide atmosphere. They react to form alkanes when treated with compounds containing active hydrogen, such as water. Organozinc compounds also react with carbonyl compounds like aldehydes and ketones to form primary, secondary, or tertiary alcohols depending on the carbonyl compound. Upon hydrolysis, the initial addition products produce the corresponding alcohols.

1. Chemistry Assignment

2. INTRODUCTION :
Organozinc compounds were developed by Frankland in 1849. They are less
reactive than Grigrand reagent and could be useful synthetic agents in certain
situations, but this use is severely limited due to their spontaneos
inflammability.
Preparation :
Organozinc compounds can be prepared by heating freshly prepared zinc
fillings with alkyl halide in an atmosphere of carbon dioxide.
RX + ZN R – Zn – X
2R – Zn – X Zn + Zn
For example,
I + Zn 𝐶2 𝐻5 - Zn – I
2C2H5 – Zn – I (C2H5)2
𝐶𝑂2
𝑅2 𝑋2
Heat
𝐶2𝐻5
𝐶𝑂2
Heat

3. Reaction :
1. Formation of alkanes : Dialkyl zinc reacts with compounds contaning active
hydrogen forming alkane.
Zn(C2H5)2 + 2H2O 2C2H6 + Zn(OH)2
(Diethylzinc) (Ethane)
Zn(C2H5)2 + 2H20 2C2H6 + (C2H5O)2 Zn
(Diethyl zinc) (Ethane) (Zinc ethylate)
2. With carbonyl compounds : It gives primary, secondary or tertiary alchohol.
A. With formaldehyde : Dialkyl zinc reacts with formaldehyde giving an
addition product which on hydrolysis gives primary alchohol.
O OH OH
H – C – H + CH3 – Zn – CH3 → H- C – H - H + Zn CH3
(Frmaldehyde) CH3 (Aduct) (Ethanol)

4. B. With other aldehydes : Dialkyl zinc reacts with other aldehydes giving an addition
product which on hydrolysis gives secondary alchohol.
O OZnCH3 HOH OH
CH3 – C – H + CH3 – Zn = CH3 → CH3 - C – H CH3 – C – H + Zn
CH3 CH3
(acetaldehyde) (Adduct) (Isopropyl alchohol)
C. WITH KETONE : Dialkyl zinc reacts with ketone giving an addition product which
on hydrolysis gives tertiary alcohol.
O OZnCH3 OH OH
CH3 – C – CH3 + CH3 – Zn – CH3 CH3 – C – H CH3 – C – H + Zn
CH3 CH3 CH3
(Acetone) (Adduct) (Tert. Butyl alcohol)