Protecting group
Acetal
Stable to base, nucleophiles, reducing agents. Removed by acid.
Protecting group
Octet web edition
Octet
Look up pKa, IR, H NMR, C NMR, and protecting-group reference records.
83Reactions
63Reagents
25Groups
109Reference rows
0Saved
0%Quiz accuracy
pKa
Acetic acid (CH₃COOH)
4.76
pKa4.76
pKa
Acetone (α-H)
Enolizable
pKa20
pKa
Acetonitrile (α-H)
25
pKa25
Protecting group
Acetyl
Forms ester (for OH) or amide (for NH₂). Removed by base hydrolysis.
Protecting group
pKa
Acetylene (≡C-H)
Terminal alkyne
pKa25
IR
Acyl halide C=O
1795-1815
IR1795-1815
IR
Alcohol O-H
3200-3600
IR3200-3600
H NMR
Aldehyde (R-CHO)
9.5-10.0
H NMR9.5-10.0
IR
Aldehyde C-H
2700-2850
IR2700-2850
IR
Aldehyde C=O
1720-1740
IR1720-1740
pKa
Alkane (C-H)
Essentially non-acidic
pKa~50
IR
Alkane C-H (sp³)
2850-3000
IR2850-3000
pKa
Alkene (=CH)
~44
pKa~44
IR
Alkene =C-H (sp²)
3000-3100
IR3000-3100
IR
Alkene C=C
1620-1680
IR1620-1680
IR
Alkyne ≡C-H (sp)
3300
IR3300
IR
Alkyne C≡C
2100-2260
IR2100-2260
H NMR
Allylic (C=C-CH)
1.6-2.0
H NMR1.6-2.0
IR
Amide C=O
1630-1690
IR1630-1690
IR
Amide N-H
3150-3400
IR3150-3400
H NMR
Amide N-H
5-8
H NMR5-8
IR
Anhydride C=O
1740-1840
IR1740-1840
H NMR
Ar-OH (phenol)
4-8
H NMR4-8
C NMR
Aromatic C (general)
110-160
C NMR110-160
C NMR
Aromatic C-C (ipso)
125-150
C NMR125-150
IR
Aromatic C-H
3000-3100
IR3000-3100
C NMR
Aromatic C-H
110-130
C NMR110-130
C NMR
Aromatic C-O
150-165
C NMR150-165
IR
Aromatic C=C
1450-1600
IR1450-1600
H NMR
Benzene ring
6.5-8.5
H NMR6.5-8.5
pKa
Benzoic acid
4.2
pKa4.2
Protecting group
Benzyl
Stable to base and mild acid. Removed under hydrogenation.
Protecting group
H NMR
Benzylic (Ar-CH)
2.2-2.5
H NMR2.2-2.5
C NMR
C-N (amine)
30-65
C NMR30-65
C NMR
C-O (alcohol, ether)
50-90
C NMR50-90
IR
C-O (alcohols, ethers)
1050-1150
IR1050-1150
IR
C-O (esters)
1000-1300
IR1000-1300
C NMR
C-X (halide)
10-75
C NMR10-75
C NMR
C=C (alkene)
100-150
C NMR100-150
C NMR
C=O (aldehyde)
190-205
C NMR190-205
C NMR
C=O (amide)
160-180
C NMR160-180
C NMR
C=O (carboxylic acid)
170-185
C NMR170-185
C NMR
C=O (ester)
160-175
C NMR160-175
C NMR
C=O (ketone)
195-220
C NMR195-220
C NMR
C≡C (alkyne)
65-90
C NMR65-90
C NMR
C≡N (nitrile)
115-125
C NMR115-125
H NMR
Carboxylic acid (R-COOH)
10-12
H NMR10-12
IR
Carboxylic acid C=O
1700-1725
IR1700-1725
IR
Carboxylic acid O-H
2500-3300
IR2500-3300
IR
Conjugated C=O
1665-1685
IR1665-1685
H NMR
Electron-poor aromatic
7.5-8.5
H NMR7.5-8.5
H NMR
Electron-rich aromatic
6.5-7.5
H NMR6.5-7.5
IR
Ester C=O
1735-1750
IR1735-1750
pKa
Ethanol
16
pKa16
pKa
Ethyl acetate (α-H)
Ester enolate
pKa25
Protecting group
Fluorenylmethyloxycarbonyl
Removed by base (not acid). Orthogonal to Boc. Standard in solid-phase peptide synthesis.
Protecting group
pKa
H₂ (dihydrogen)
35
pKa35
pKa
H₂CO₃
Carbonic acid
pKa6.4
pKa
H₂O
OH⁻
pKa15.7
pKa
H₂S
7
pKa7
pKa
H₂SO₄
First proton
pKa-3
pKa
H₃O⁺
Hydronium ion
pKa-1.7
pKa
HBr
-9
pKa-9
pKa
HCl
-7
pKa-7
pKa
HCN
Hydrogen cyanide
pKa9.2
pKa
HF
Weak due to strong H-F bond
pKa3.2
pKa
HI
Strongest common acid
pKa-10
pKa
HNO₃
-1.4
pKa-1.4
pKa
HSO₄⁻
Second proton of H₂SO₄
pKa2
IR
Imine C=N
1640-1690
IR1640-1690
H NMR
Internal alkene (=CHR)
5.2-5.7
H NMR5.2-5.7
IR
Ketone C=O
1705-1725
IR1705-1725
Protecting group
Methyl ester
Simple protection. Easily hydrolyzed back to acid.
Protecting group
pKa
NH₃
NH₂⁻
pKa38
pKa
NH₄⁺
Ammonium ion
pKa9.2
IR
Nitrile C≡N
2200-2260
IR2200-2260
IR
Nitro N=O
1515-1560 & 1345-1385
IR1515-1560 & 1345-1385
pKa
Phenol (ArOH)
Resonance into ring stabilizes anion
pKa10
IR
Phenol O-H
3200-3600
IR3200-3600
IR
Primary amine N-H
3300-3500
IR3300-3500
H NMR
Propargylic (C≡C-CH)
1.8-2.2
H NMR1.8-2.2
C NMR
R-CH₃
0-30
C NMR0-30
H NMR
R-CH₃ (primary alkyl)
0.9-1.0
H NMR0.9-1.0
H NMR
R-NH₂ (amine)
0.5-3
H NMR0.5-3
H NMR
R-OH (alcohol)
1-5
H NMR1-5
C NMR
R₂CH₂
15-55
C NMR15-55
H NMR
R₂CH₂ (secondary alkyl)
1.2-1.4
H NMR1.2-1.4
C NMR
R₃CH
20-60
C NMR20-60
H NMR
R₃CH (tertiary alkyl)
1.4-1.7
H NMR1.4-1.7
C NMR
R₄C
30-45
C NMR30-45
pKa
RCOOH (carboxylic acid)
Resonance-stabilized anion
pKa4-5
pKa
RNH₂ (amine)
35-40
pKa35-40
pKa
RNH₃⁺
Protonated amine
pKa10-11
pKa
ROH (alcohol)
RO⁻
pKa16-18
pKa
RSH (thiol)
More acidic than alcohol
pKa10-11
IR
S-H (thiol)
2550-2600
IR2550-2600
IR
Secondary amine N-H
3300-3500
IR3300-3500
pKa
t-Butanol
Bulky, less acidic
pKa18
H NMR
Terminal alkene (=CH₂)
4.6-5.0
H NMR4.6-5.0
H NMR
Terminal alkyne (≡C-H)
1.8-3.0
H NMR1.8-3.0
Protecting group
tert-Butoxycarbonyl
Common in peptide synthesis. Orthogonal to Fmoc.
Protecting group
Protecting group
tert-Butyldimethylsilyl
Very common. Stable to many conditions. Removed by fluoride.
Protecting group
Protecting group
Tetrahydropyranyl
Creates acetal. Stable to base. Introduces chirality (diastereomers).
Protecting group
H NMR
Vinyl H (C=CH)
4.5-6.5
H NMR4.5-6.5
H NMR
α to C=O (ketone/aldehyde)
2.0-2.5
H NMR2.0-2.5
H NMR
α to halogen (R-CHX)
3.0-4.0
H NMR3.0-4.0
H NMR
α to nitrogen (R-CH₂-N)
2.2-2.8
H NMR2.2-2.8
H NMR
α to oxygen (R-CH₂-O)
3.4-4.0
H NMR3.4-4.0