All values in δ (ppm), referenced to tetramethylsilane (TMS, δ = 0).

Proton Environment	Typical δ Range	Note
Alkyl C–H, not adjacent to a functional group	0.9–1.5	Baseline aliphatic region
C–H adjacent to C=O, C=C, or aromatic ring (allylic/benzylic)	2.0–2.5	Slightly deshielded by the adjacent π system
C–H adjacent to a halogen	3.0–4.0	Deshielded by the electronegative halogen
O–CH₂/O–CH₃ (ether or ester alkyl group)	3.3–4.5	Deshielded by the adjacent oxygen
Alcohol O–H	1–5 (variable)	Broad; position shifts with concentration and hydrogen bonding; exchangeable
Vinyl C–H (alkene)	4.5–6.5	—
Aromatic C–H	6.5–8.5	Deshielded by the aromatic ring current
Amine N–H	1–5 (variable)	Broad; exchangeable
Amide N–H	5–8 (variable)	Broad; exchangeable
Aldehyde C–H	9.5–10.0	Highly diagnostic — appears in no other common environment
Carboxylic acid O–H	10–13	Broad; exchangeable; one of the most downfield common signals

Exchangeable protons (O–H, N–H) vary in position and often appear broadened; they can be confirmed by shaking the sample with D₂O, which causes the signal to disappear (Chapter 19).

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