Hydroxybenzaldehydes

Hydroxybenzaldehydes
Surname	2-hydroxybenzaldehyde	3-hydroxybenzaldehyde	4-hydroxybenzaldehyde
other names	o -hydroxybenzaldehyde, 2-formylphenol, salicylaldehyde	m -hydroxybenzaldehyde, 3-formylphenol	p -hydroxybenzaldehyde, 4-formylphenol
Structural formula
CAS number	90-02-8	100-83-4	123-08-0
PubChem	6998	101	126
Molecular formula	C 7 H 6 O 2
Molar mass	122.13 g mol −1
Physical state	liquid	firmly
Melting point	−7 ° C	104 ° C	116-117 ° C
boiling point	197 ° C	240 ° C
pK s value	6.79	8.00	7.66
GHS labeling	Caution	Caution	Caution
H and P phrases	302-315-319-335	315-319-335	315-319-335
	no EUH phrases	no EUH phrases	no EUH phrases
	261-302 + 352 305 + 351 + 338-321-405-501	261-305 + 351 + 338	261-305 + 351 + 338

In chemistry, hydroxybenzaldehydes form a group of substances that are derived from both benzaldehyde and phenol . The structure consists of a benzene ring with attached aldehyde  (-CHO) and hydroxyl group  (-OH) as substituents . Their different arrangements ( ortho , meta or para ) result in three constitutional isomers with the empirical formula C ₇ H ₆ O ₂ . They are mainly to be regarded as derivatives of benzaldehyde. 2-Hydroxybenzaldehyde is known by its common name, salicylaldehyde .

properties

The hydroxybenzaldehydes have (9.99) is significantly lower compared to the phenolic pK _s values ; the electron-withdrawing aldehyde group ( −M effect ) increases the acidity; the phenolic OH bond is increasingly polarized.

Individual evidence

1. ↑ ^{a b c} Entry on salicylaldehyde in the GESTIS substance database of the IFA , accessed on August 19, 2012(JavaScript required) .
2. ↑ ^{a b c d e f} CRC Handbook of Tables for Organic Compound Identification , Third Edition, 1984, ISBN 0-8493-0303-6 .
3. ↑ Data sheet 3-Hydroxybenzaldehyde from Sigma-Aldrich , accessed on May 3, 2011 ( PDF ).
4. ↑ Data sheet 4-Hydroxybenzaldehyde from Sigma-Aldrich , accessed on May 3, 2011 ( PDF ).

See also

• Hydroxybenzyl alcohols
• Hydroxybenzoic acids