How did Claude Debussy use the whole-tone scale to weaken a sense of key?

Claude Debussy utilized the whole-tone scale—a sequence of notes separated entirely by whole steps—to dissolve the traditional sense of key and functional tonality in his compositions.12

By employing this scale, Debussy effectively weakened harmonic structure in several ways:

• Absence of Resolution: Because the whole-tone scale lacks the semitones found in major and minor scales, it eliminates the leading tones and dominant harmonies necessary for traditional resolution. Consequently, chords built from this scale cannot resolve to the stable harmonies expected in the common practice period.12
• Augmented Triads: All triads derived from the whole-tone scale are augmented, creating a dissonant, unstable sound that lacks the perfect fourths and fifths that serve as the traditional cornerstones of harmony.2
• Suspension of Tonality: By removing the distribution of whole and half steps that define traditional keys, Debussy created music that exists without a clear harmonic center. In works such as "Voiles," this allows the music to function through melodic emphasis and repetition rather than traditional harmonic progression.12

This approach allowed Debussy to treat chords for their coloristic value, effectively blurring the outlines of traditional harmonic movement.2