The melting points of the product and 2,5-dichloro-2,5-dimethylhexane are around 62-64°C and 63-64°C respectively. Since the temperature ranges are very close, it shows the presence of 2,5-dichloro-2,5-dimethylhexane.
In IR spectrum, the OH peak is missing from the spectrum of the product. It shows the absence of 2,5-dimethyl-2,5-hexandiol, as the alcohol was converted to 2,5-dichloro-2,5-dimethylhexane.