Question
Give information about $C-O-H$ bond angle in alcohol, phenol and ether with suitable example.
✓
Answer
$\rightarrow$ In alcohols, the oxygen of $-OH$ group is attached to carbon by a sigma $(\sigma)$ bond formed by the overlap of an $sp^3$ hybridised orbital of carbon with $sp^3$ hybridised orbital of oxygen.
$\rightarrow$ Figure depicts structural aspects of methanol, phenol and methoxymethane.
$\rightarrow$ The bond angle
in alcohols is slightly less than the tetrahedral angle $(109^\circ -28 \ ').$
$\rightarrow$ It is due to the repulsion between the unshared electron pairs of oxygen.
$\rightarrow$ In phenols, the $OH$ group is attached to $sp^2$ hybridised carbon of an aromatic ring.
$\rightarrow$ The carbon$-$oxygen bond length $(136 \ pm)$ in phenol is slightly less than that in methanol.
$\rightarrow$ This is due to $(i)$ partial double bond character on account of the conjugation of unshared electron pair of oxygen with the aromatic ring and $(ii) \ sp^2$ hybridised state of carbon to which oxygen is attached.
$\rightarrow$ In ethers, the four electron pairs, i.e., the two bond pairs and two lone pairs of electron on oxygen are arranged approximately in a tetrahedral arrangement.
$\rightarrow$ The bond angle is slightly greater than the tetrahedral angle due to the repulsive interaction between the two bulky $(-R)$ groups.
$\rightarrow$ The $C-O$ bond length $(141\ pm)$ is almost the same as in alcohols.
$\rightarrow$ Figure depicts structural aspects of methanol, phenol and methoxymethane.
$\rightarrow$ The bond angle
in alcohols is slightly less than the tetrahedral angle $(109^\circ -28 \ ').$$\rightarrow$ It is due to the repulsion between the unshared electron pairs of oxygen.
$\rightarrow$ In phenols, the $OH$ group is attached to $sp^2$ hybridised carbon of an aromatic ring.
$\rightarrow$ The carbon$-$oxygen bond length $(136 \ pm)$ in phenol is slightly less than that in methanol.
$\rightarrow$ This is due to $(i)$ partial double bond character on account of the conjugation of unshared electron pair of oxygen with the aromatic ring and $(ii) \ sp^2$ hybridised state of carbon to which oxygen is attached.
$\rightarrow$ In ethers, the four electron pairs, i.e., the two bond pairs and two lone pairs of electron on oxygen are arranged approximately in a tetrahedral arrangement.
$\rightarrow$ The bond angle is slightly greater than the tetrahedral angle due to the repulsive interaction between the two bulky $(-R)$ groups.
$\rightarrow$ The $C-O$ bond length $(141\ pm)$ is almost the same as in alcohols.
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